To see the other types of publications on this topic, follow the link: Abrasion.
Dissertations / Theses on the topic 'Abrasion'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Abrasion.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Popa, Mihaela. "Tooth cleaning : abrasive particles but no abrasion." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI034.
Full textAbstract:
En 1997 Stuard L. Fischman a dit « Certainement on mange bien, on parle bien, on a l'air bien et on « sent frais » - mais on a aussi la plaque dentaire, la gingivite et les caries dentaires. Le lecteur peut déterminer les progrès réalisés en réfléchissant à son état de santé bucco-dentaire personnel! ». Vingt ans plus tard cette affirmation reste valide. L'acte le plus commun d'hygiène buccale est de se nettoyer les dents par brosse à dents, eau et dentifrice. Le rôle principal de la brosse à dents et du dentifrice est d'éliminer le biofilm dentaire responsable des maladies buccales. Il est largement admis que le biofilm dentaire est éliminé au moyen de particules de nettoyage trouvés dans la composition du dentifrice. Puisque le mécanisme des particules nettoyantes est couramment supposé abrasif, la recherche sur le nettoyage des dents a été principalement conduite du point de vue « abrasif », elles sont ainsi appelées « particules abrasives ». Néanmoins, le nettoyage des dents est un processus complexe impliquant plusieurs mécanismes (biochimiques, physico-chimiques et mécaniques), chacun activé par des facteurs à la fois internes (comme l'environnement oral individuel et les habitudes individuelles d'hygiène buccale) et externes La conception de la brosse à dents et la composition de dentifrice). Ce travail a commencé à partir de l'idée que le nettoyage des dents ne peut pas être réduit à un processus d'abrasion; par conséquence, afin d'acquérir une connaissance plus profonde du comportement réel des particules nettoyantes, il est nécessaire de comprendre la contribution de chaque mécanisme d'action impliqué. Un système biomimétique a été développé pour reproduire la brosse à dents, l'émail dentaire, la pellicule exogène acquise et le dentifrice (une suspension simplifiée à base de silice). Le système a été analysé d'un point de vue tribologique, en adoptant la théorie du « troisième corps » et en utilisant différentes techniques expérimentales (spectroscopie infrarouge, microscopie à force atomique, la microscopie électronique à balayage). On a déterminé la contribution de la mécanique et de la physico-chimie de la surface de l'émail dentaire, de la chimie du dentifrice et de la mécanique de la brosse à dents. Les résultats ont montré que la pellicule exogène acquise biomimétique n'a pas été rayée pendant le nettoyage des dents, mais plutôt lissée ou enlevée, ce qui suggère que l'abrasion n'est pas le mécanisme «gouvernant» du processus de brossage des dents. En effet, un mécanisme de «lubrification fractionnée» est supposé intervenir, favorisant la formation des agglomérats de silice supportent la charge normale dans des zones de contact localisées. L'efficacité du processus de nettoyage des dents est censée être contrôlée par la taille des agglomérats de silice, qui dépend à son tour de la mécanique et la physico-chimie de la surface de l’émail dentaire, de la chimie du dentifrice et de la mécanique de la brosse à dents<br>In 1997, Stuart L. Fischman wrote “We certainly eat well, speak well, look fine and ‘smell fresh’—but we also have plaque, gingivitis and dental caries. The reader can determine how much progress has been made by reflecting on his or her personal oral health status!” Two decades later, this affirmation is still valid. The most common act of oral hygiene is to clean one’s teeth via toothbrush, water, and dentifrice. The main role of toothbrush and dentifrice is to remove the dental biofilm responsible for oral diseases. Over the years, several studies have focused on improving toothbrushing techniques, toothbrush design, and dentifrice composition, often leading to conflicting results. It is largely accepted that dental biofilm is removed by means of cleansing particles, which can be found in many dentifrice compositions. Since the mechanism of the cleansing particles is commonly believed to be abrasive, research on teeth cleaning has been mainly conducted from an ‘abrasive’ point of view, so much so that cleansing particles are frequently referred to as ‘abrasive particles’. Nonetheless, teeth cleaning is a complex process involving several mechanisms (bio-chemical, physico-chemical, and mechanical), each one activated by factors that are both internal (such as individual oral environment and individual oral hygiene habits) and external (such as toothbrush design and dentifrice composition). This work started from the idea that teeth cleaning cannot be reduced to an abrasion process; consequently, in order to gain deeper knowledge about the actual behavior of the cleansing particles, it is necessary to understand the contribution of each mechanism involved. A biomimetic system was developed to reproduce toothbrush, dental enamel, acquired enamel pellicle, and dentifrice (modeled as a silica-based slurry). The system was analyzed from a tribological point of view, adopting the ‘third-body approach’ and employing different experimental techniques such as infrared spectroscopy, atomic force microscopy, and environmental scanning electron microscopy. The contribution of the dental enamel surface mechanics and physico-chemistry, of the dentifrice chemistry, and of toothbrush mechanics was assessed. Results showed that the biomimetic acquired enamel pellicle was not scratched during teeth cleaning, but rather smoothened or removed, suggesting that abrasion is not the governing mechanism of the toothbrushing process. Indeed, a ‘fractionated lubrication’ mechanism is believed to take part, promoting the formation of silica agglomerates that bear normal load at localized contact areas. The effectiveness of the teeth cleaning process is believed to be controlled by the size of the silica agglomerates, which in turn depends on dental enamel surface mechanics and physico-chemistry, dentifrice chemistry, and toothbrush mechanics
2
Kelly, Damian Anthony. "Abrasion in oral care." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619939.
Full text
3
Sadegzadeh, Massud. "Abrasion resistance of concrete." Thesis, Aston University, 1985. http://publications.aston.ac.uk/14253/.
Full textAbstract:
This thesis describes an experimental study of the abrasion resistance of concrete at both the macro and micro levels. This is preceded by a review related to friction and wear, methods of test for assessing abrasion resistance, and factors influencing the abrasion resistance of concrete. A versatile test apparatus was developed to assess the abrasion resistance of concrete. This could be operated in three modes and a standardised procedure was established for all tests. A laboratory programme was undertaken to investigate the influence, on abrasion resistance, of three major factors - finishing techniques, curing regimes and surface treatments. The results clearly show that abrasion resistance was significantly affected by these factors, and tentative mechanisms were postulated to explain these observations. To substantiate these mechanisms, the concrete specimens from the macro-study were subjected to micro-structural investigation, using such techniques as 'Mercury Intrusion Forosimetry, Microhardness, Scanning Electron Microscopy, Petrography and Differential Thermal Analysis. The results of this programme clearly demonstrated that the abrasion resistance of concrete is primarily dependent on the microstructure of the concrete nearest to the surface. The viability of indirectly assessing the abrasion resistance was investigated using three non-destructive techniques - Ultrasonic Pulse Velocity, Schmidt Rebound Hardness, and the Initial Surface Absorption Test. The Initial Surface Absorption was found to be most sensitive to factors which were shown to have influenced the abrasion resistance of concrete. An extensive field investigation was also undertaken. The results were used to compare site and laboratorypractices, and the performance in the accelerated abrasion test with the service wear. From this study, criteria were developed for assessing the quality of concrete floor slabs in terms of abrasion resistance.
4
Ribeiro, Vilmondes. "Abrasividade pendular e a resistência mecânica das rochas." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3134/tde-20082010-164048/.
Full textAbstract:
A interação entre rocha e metal, na forma de operações como perfuração, escavação e cominuição, dá origem a dois efeitos: um desejado, desagregação da rocha e outro indesejado, desgaste do metal. Como o desgaste, dramaticamente, influencia o desempenho dos equipamentos, é fundamental para estabelecer uma base para equações de predição de taxas de desgaste potencial. Neste contexto, Golovanevskiy e Bearman (2008), propuseram mais um método para avaliação da abrasividade. Este método, ensaio de abrasão por impacto deslizante (Gouging Abrasion Test), é realizado em condições de alta tensão/alto impacto de desgaste e é caracterizado pela maior taxa de remoção de material de todos os modos de desgaste e, portanto, representa o modo mais severo de desgaste abrasivo.O método consiste, basicamente, de uma ponteira cilíndrica com uma ponta cônica de 90º. Esta ponteira, em trajetória pendular, atinge uma amostra de rocha com energia de impacto de aproximadamente 300 joules e velocidade da ordem de 5,2 m/s. Semelhante à metodologia de cálculo de abrasividade Cerchar (CAI), o Gouging Abrasion Index (Gi) é calculado como sendo a média do diâmetro da ponta cônica, após desgaste, em milímetros e multiplicado por 10. Este trabalho verificou a adequabilidade do Gouging Abrasion Test, para um pequeno número de amostras de rocha que representam, qualitativamente, os principais tipos de rocha encontrados no Brasil e a sua correlação com outros ensaios consagrados como resistência à compressão, desgaste Amsler e dureza Knoop. Está análise mostrou alta correlação entre Gi e dureza knoop (R² = 0,94), baixa correlação com desgaste Amsler (R² = 0,41) e nenhuma correlação com resistência à compressão uniaxial.<br>The rock-metal interaction, like occurs in operations as drilling, excavation and crushing, generates two effects: the desired rock degradation and the undesirable metal wear. As the wear dramatically influences the process performance of the equipment, it is critical to establish a basis for predictive equations to estimate potential wear rates. Following this context, in 2008 Golovanevskiy and Bearman proposed a method for abrasiveness evaluation. The method, Gouging Abrasion Test, employs high-stress load gouging/sliding impact wear and is characterized by the highest material removing rate than all wear modes, therefore representing the most severe type of abrasive wear. The method consists, in a few words, of a steel wear tool with a 90o sharp conical tip. This tip attacks a rock sample in a swinging trajectory with a impact energy of more than 300 joules and a speed around 5,2 m/s. Like the Cerchar Abrasivity Index (CAI) calculation, the Gouging Abrasion Index (Gi) is determined as 10 times de average diameter in millimeters of de conical tip (now flat) after one event of wear. This work intends to improve the knowledge about Gouging Abrasion Test, and evaluates its suitability in a small group of rocks that represents some of the main types to be found in Brazil\'s rock cutting, drilling and crushing works. Its relation to other frequent tests like uniaxial compressive strength, Amsler abrasive wear and Knoop hardness were also verified. The results show high correlation between Gi and Knoop hardness (R2 = 0,94), low correlation with Amsler wear (R2 = 0,41) and no relation to uniaxial compressive strength.
5
Wu, Guangchang. "The mechanisms of rubber abrasion." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/25986.
Full textAbstract:
Rubber abrasion is one of the most important properties for rubber products, such as tyres. However, due to its complexity rubber abrasion is still a very challenging topic in rubber research. Rubber abrasion is not governed by a single mechanism. Different mechanisms can dominate the abrasion behaviour depending on the rubber compound, base polymer type, loading severity, contact conditions, testing temperature and chemical environment. This study investigates the different mechanisms for rubber abrasion and the transition between these mechanisms using two types of abrasion apparatus, a blade abrader and a surface abrader, respectively. Blade abrasion was used to generate the abrasion pattern. Once the abrasion pattern was formed on the rubber surface under unidirectional sliding, the underlying mechanism was primarily one of fatigue crack growth, which is referred as "fatigue wear" in the literature. An independent pure shear fatigue test with various loading profiles was conducted to predict the crack growth rate using a fracture mechanics approach during these abrasion tests. The tearing energy during blade abrasion was calculated using a fracture mechanics approach. A Finite Element Analysis (FEA) technique using the Virtual Crack Closure Technique (VCCT) was adopted. The VCCT approach was a simpler, faster and more reliable approach to derive the tearing energy under these complicated large strain contact conditions. The prediction of the abrasion rate using this independent measurement of the crack growth resistance of materials worked best for unfilled SBR material. A bespoke surface contact abrasion machine was used to investigate rubber abrasion on silicon carbide sandpaper under both dry and wet conditions. Depending on the materials, contact conditions and sliding velocity, two different mechanisms were observed. The first being a mechanochemical degradation, during which a sticky layer was generated on the rubber surface. This behaviour is also called "smearing wear". The second failure mode resulted from a purely mechanical fracture named "abrasive wear". It seemed that the carbon black filled rubber was more susceptible to smearing wear than the silica filled one. Higher sliding velocities promoted smearing wear, possibly due to higher temperatures being generated at the interface. Alternatively, water lubrication was seen to promote abrasive wear. Therefore, the abrasion mechanism changed to more rapid abrasive wear under wet conditions, which resulted in a significant increase in the rate of weight loss. Finally, the sticky debris generated during the smearing wear was characterised using various different techniques. This revealed that the sticky debris had more oxygen and lower carbon and sulphur content. It contained a greater amount volatiles and generated more char formation during its degradation in the air. The molecular weight of the sticky debris was much lower when compared to the original uncured rubber. It seemed that in the sticky debris the filler network can slowly recover and the degraded polymer chains can re-absorb back onto filler surface forming "bound rubber", which leads to faster rates of weight loss.
6
Cozza, Ronaldo Câmara. "Estudo do comportamento do coeficiente de desgaste e dos modos de desgaste abrasivo em ensaios de desgaste micro-abrasivo." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-31032008-101929/.
Full textAbstract:
Esta Dissertação tem por objetivo estudar o comportamento de diferentes materiais sob a ação de desgaste micro-abrasivo. Como parte do trabalho, foi projetada e construída uma máquina de ensaio desgaste por micro-abrasão por esfera rotativa fixa, com configuração mecânica com diferenças em relação às observadas na literatura (Gee et al., 2005). Como corpos-de-prova, foram utilizadas pastilhas intercambiáveis de metal duro (classe P20) e aço ferramenta M2. As esferas foram de aço AISI 1010 cementado e aço AISI 52100 temperado e revenido. Durante os ensaios, foi inserida entre a esfera e o corpo-de-prova uma pasta abrasiva preparada com carbeto de silício preto, com tamanho médio de partícula de 5 µm. Inicialmente, foram realizados ensaios preliminares, com a finalidade de analisar não só o comportamento do equipamento, mas também estudar a transição entre os modos de desgaste que podem ocorrer durante o desgaste micro-abrasivo. A transição entre os modos de desgaste foi estudada em função da carga normal e dos materiais utilizados durante o ensaio. Os resultados obtidos indicaram boa reprodutibilidade do equipamento e coerência com resultados da literatura. Em seguida, em ensaios denominados definitivos, foram pesquisadas as atuações dos modos de desgaste abrasivo e a obtenção do regime permanente de desgaste. Os resultados mostraram que, com a variação da distância de deslizamento, houve alterações nas ocorrências dos modos de desgaste abrasivo. Por outro lado, em alguns ensaios, o coeficiente de desgaste tendeu a permanecer constante, o que caracteriza a obtenção do regime permanente de desgaste. Entretanto, em outros, o coeficiente de desgaste teve uma evolução aleatória com a distância de deslizamento, fornecendo indicativos de que o desgaste não entrou em regime.<br>This work presents a study on the behavior of different materials under the action of micro-abrasive wear. A micro-abrasive wear testing machine with fixed sphere was designed and constructed, presenting a mechanical configuration with differences with respect to those found in the literature (Gee et al., 2005). M2 tool steel and WC-Co P20 were used as testing specimen materials. Ball materials were cemented AISI 1010 steel and quenched and tempered AISI 52100 steel. During the tests, an abrasive slurry, prepared with black silicon carbide (SiC) particles (average particle size of 5 µm), was supplied to the contact between the specimen and the ball. Initially, preliminary tests were conducted to study the wear mode transitions that can occur during the micro-abrasive wear and to analyze the operational conditions of the equipment. The wear mode transitions were evaluated as a function of the applied normal load and of the materials used. The results indicated good reproducibility and qualitative agreement with those found in the litarature. Later, a new set of tests was conducted, which analyzed the evolution of the abrasive wear modes and the achievement of steady state wear as a function of sliding distance. The results indicated a continuous variation in the abrasive wear modes with sliding distance. Additionally, in some tests, the wear coefficient tended to stabilize in constant value, which characterizes the achievement of steady state regime. However, in other tests, the wear coefficient presented a non constant evolution of wear coefficient with the sliding distance, which denotes that the constant regime of wear was not obtained.
7
Doan, Yen The. "Experimental investigation and wear simulation of three-body abrasion." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-158239.
Full textAbstract:
The wear process in three-body contact causes problems of abrasion such as volume loss and changes of geometry of the triboelements. The wear problem leads to increased failure and high costs for repairing or replacing equipment. To understand the nature of the wear behaviour and to predict the wear rate in advance, experimental investigation and numerical simulation of the wear process are required.
In this work, the wear process is analysed and the influencing parameters governing the wear behaviour are investigated experimentally to develop a new wear model. Main influential factors are considered such as kinematics of abrasive particles, contact stiffness of the particle layer, friction characteristics, and wear factors. The experiments to study kinematics of particle layers are performed on a new observation tester. To define the contact stiffness of abrasive particles, experiments are conducted by the uniaxial spindle compression tester. Moreover, a tribometer test rig with applied load up to 200 N and velocity up to 1000 mm/s is used to investigate the friction characteristics and the wear behaviour of three-body tribosystem.
Analyses of influential factors on the wear behaviour in dependency of predefined process parameter are carried out. Additionally, based on the results of the experimental investigations, approximation equations representing the relation of the influential factors and the process parameters are determined. A three-body wear model is build up to represent the wear behaviour by physical wear laws. Furthermore, these approximation equations and the relevant parameters obtained by experimental investigations are included in the Fleischer’s wear equation to simulate the wear process.
With the coupled model the wear process of the sample can be simulated twodimensional over the sliding distance. It is possible to predict the wear depth and the wear intensity, which can be used to estimate the wear rate. Additionally, from the results of the wear simulation the worn surface and the local contact pressure in the contact region are determined which provide a deeper insight into the wear process.
With this simulation the understanding of the wear behaviour can be improved which is important to solve wear problems.
8
Evans, Paul Done. "The hardness and abrasion of polymers." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38305.
Full text
9
Liang, Hancheng. "Investigating the mechanism of elastomer abrasion." Thesis, Queen Mary, University of London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582606.
Full textAbstract:
This study aims to understand the mechanism of elastomer abrasion using Finite Element Analysis (FEA) techniques. A blade abrasion device is used to create the abrasion patterns. The initiation of the abrasion patterns is investigated by observing how the cracks develop on the moulded flat elastomer surface. At first, cracks initiate at the location of the maximum tensile stress, yielding a crack growth angle of between 30o~50° with the elastomer surface. The angle being greater as the normal load applied on the blade is increased. The crack growth angle reduces as the crack increases in length. It passes through several steps, each with a reduced crack growth angle and eventually reaches a much smaller angle generally observed at the steady state of abrasion. This initial crack growth process is predicted well by the FEA simulation. Both the experimental and the computed results suggest that the initial cracks in elastomer abrasion originate from micro-vibrations generated during the slip phase of stick-slip motion. This stick-slip motion is regularly encountered during the frictional contact between a soft elastomer and hard abrader. The propagation of the abrasion patterns after reaching steady state is also investigated using a blade abrasion device. The second part of this investigation examines the effect of the normal and frictional forces on the rate and direction of crack growth during the abrasion process. Comparison is drawn between the rates of material loss as measured experimentally under a range of test conditions and the predictions calculated using a fracture mechanics based FEA. For the first time here it is shown that an explicit dynamic FEA model can be used to reliably predict the stored energy release rate in a complicated large strain contact model. A series of different finite element models were developed to investigate the tearing processes at a specific asperity under each revolution or pass of the abrasion blade. These models predict for SBR materials the rate of the resulting tearing processes well.
10
Cozza, Ronaldo Câmara. "Estudo do desgaste e atrito em ensaios micro-abrasivos por esfera rotativa fixa em condições de força normal constante e pressão constante." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-26082011-143752/.
Full textAbstract:
O ensaio de desgaste micro-abrasivo por esfera rotativa vem conquistando elevada aceitação em universidades e centros de pesquisa, sendo amplamente adotado em estudos envolvendo desgaste abrasivo de materiais. Dois modos de desgaste abrasivo podem ser observados neste tipo de ensaio: rolamento resulta quando as partículas abrasivas rolam sobre a superfície do corpo-de-prova, enquanto riscamento é observado quando as partículas abrasivas deslizam sobre o mesmo; o tipo do modo de desgaste abrasivo apresenta uma significante influência sobre o comportamento de um sistema tribológico. Diversos trabalhos envolvendo coeficiente de atrito durante ensaios de desgaste abrasivo estão disponíveis na literatura, mas somente uma pequena parcela dedicaram-se ao estudo do coeficiente de atrito desenvolvido em ensaios de desgaste micro-abrasivo conduzidos por esfera rotativa. Adicionalmente, pesquisas preliminares reportaram que os resultados são dependentes da variação de pressão, ocasionada pela condução de ensaios sob condições de força normal constante. Logo, o propósito desta Tese de Doutorado é pesquisar a relação entre coeficiente de atrito e modos de desgaste abrasivo em ensaios desgaste micro-abrasivo por esfera rotativa, em condições de força normal constante e pressão constante. Ensaios ball-cratering foram conduzidos com esferas de aço AISI 52100 e um corpo-de-prova de aço-ferramenta AISI H10. A pasta abrasiva foi preparada com partículas de carbeto de silício (SiC) preto (tamanho médio de partícula de 3 m) e água destilada. Diferentes valores de força normal constante e pressão constante foram definidos para os experimentos. As forças normal (N) e tangencial (T) foram monitoradas continuamente durante os ensaios e a relação entre T/N foi calculada para fornecer uma indicação do coeficiente de atrito atuante no sistema tribológico esfera / partículas abrasivas / corpo-de-prova. Em todos os casos, análises por Microscopia Óptica das crateras de desgaste revelaram somente a presença de desgaste abrasivo por riscamento. Entretanto, observações mais detalhadas, conduzidas por Microscopia Eletrônica de Varredura, indicaram que diferentes níveis desgaste abrasivo por rolamento atuaram ao longo dos riscos, fenômeno nomeado de micro-rolling abrasion (microrolamento). Além disso, os resultados obtidos mostraram, também, que: i) a distância de deslizamento apresenta significante influência sobre a transição entre os modos de desgaste abrasivo, ii) para os valores de força normal constante e pressão constante adotados, o coeficiente de atrito manteve-se, aproximadamente, na mesma faixa de valores e iii) o coeficiente de atrito é independente da taxa de desgaste.<br>The micro-scale abrasive wear test by rotative ball has gained large acceptance in universities and research centers, being widely used in studies on the abrasive wear of materials. Two wear modes are usually observed in this type of test: rolling abrasion results when the abrasive particles roll on the surface of the tested specimen, while grooving abrasion is observed when the abrasive particles slide; the type of wear mode has a significant effect on the overall behaviour of a tribological system. Several works on the friction coefficient during abrasive wear tests are available in the literature, but only a few were dedicated to the friction coefficient in micro-abrasive wear tests conducted with rotating ball. Additionally, recent works have identified that results may also be affected by the change in contact pressure that occurs when tests are conducted with constant applied force. Thus, the purpose of this work is to study the relationship between friction coefficient and abrasive wear modes in ball-cratering wear tests conducted at constant normal force and constant pressure. Micro-scale abrasive wear tests were conducted with a ball of AISI 52100 steel and a specimen of AISI H10 tool steel. The abrasive slurry was prepared with black silicon carbide (SiC) particles (average particle size of 3 m) and distilled water. Two constant normal force values and two constant pressure values were selected for the tests. The tangential and normal loads were monitored throughout the tests and their ratio was calculated to provide an indication of the friction coefficient. In all cases, optical microscopy analysis of the worn craters revelated only the presence of grooving abrasion. However, a more detailed analysis conducted by SEM has indicated that different degrees of rolling abrasion have also occurred along the grooves. The results have also shown that: i) the sliding distance presents an important role on the wear mode transition, ii) for the selected values of constant normal force and constant pressure, the friction coefficient presented, approximately, the same range of values and ii) the friction coefficient was independent of the wear rate.
11
Halley, William G. "Evaluating abrasive wear resistance of extruder tooling materials using the dry sand rubber wheel abrasion test." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42102.
Full textAbstract:
A series of experiments was performed on groups of
samples made from materials currently used to manufacture
tooling for extruders to determine if the ASTM G65 dry sand
rubber wheel abrasion test could be used as an accelerated
test to evaluate candidate materials. Samples were tested in
the heat treated condition and after surface modification by
plasma ion nitriding. The range of materials tested included
medium and high alloy steels and steel bonded carbide
composites. The abrasives used were AFS 50/70 test sand and
Dresser Glasgrain crushed fused silica.
<p>Evaluation of test wear scars and wear debris from the
tests using AFS 50/70 showed that delamination was the
primary wear mechanism for the composite materials, with some
ploughing and microcutting, while ploughing and microcutting
were the primary mechanisms in the wear of the steels.
Evaluation of parts made from a composite material which were
removed from service indicated that matrix erosion was the
primary wear mechanism. Tests with Glasgrain fused silica as
the abrasive yielded wear scars with the same morphology as
the parts returned from service, but the very poor flow
characteristics of this material caused inconsistency in the
supply of this abrasive to the contact region.
<p>Interrupted tests showed that the wear rate was constant
for the steels in the non-nitrided condition. After
nitriding, the wear rate increased with test duration. The
nitriding was found to act as a barrier coating providing an
initial period of very low wear until the nitride layer is
broached. The wear rate then increases to approximate the
wear rate of the non-nitrided samples.
<p>It was found that the friction force alters the location
of the maximum normal force, shifting the point of greatest
contact force toward the entry end of the wear scar.<br>Master of Science
12
Palanisamy, Karthikeyan. "Modeling of agglomerate abrasion in fluidized beds." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58970.
Full textAbstract:
Agglomeration occurs in fluidized beds in many industrial processes. It can be a desirable phenomenon, for instance in the pharmaceutical industries, or undesirable, as when it occurs in the Fluid Cokers used in bitumen processing. Excessive agglomerate growth can lead to a reduced efficiency of the process and ultimately to defluidization. Mathematical modeling can provide insights into agglomerate formation and breakage. Modeling the physics of agglomerate breakage is complicated since the breakage model needs to account for a number of processes occurring inside the fluidized bed. Breakage of agglomerates can happen due to fragmentation (high energy based) or abrasion (low energy based), or a combination of both. Abrasion is the process of losing one or a few of the particles from the surface of the agglomerate. It occurs continuously inside the fluidized beds and cannot be neglected for Fluid Cokers. Fragmentation, on the other hand, is the fracture of an agglomerate into pieces due to the breakage of multiple bonds inside it. In this work, a physical model that describes abrasion is derived utilizing the concepts of Kinetic Theory of Granular Flows (KTGF). The model considers the collisions between the different solid phases—particles and agglomerates to obtain the frequency of abrasion and mass transfer between the phases. A Eulerian-Eulerian formulation along with KTGF is used to simulate abrasion of a large agglomerate inside a fluidized bed. All the simulations were performed with commercial CFD code ANSYS Fluent 16, which was augmented by user-defined functions for different experimental conditions and different bed materials using published experimental data. The comparison between the modeling predictions and experimental results demonstrated a good qualitative agreement with some quantitative variations. It was found that the model tends to underestimate the amount of abrasion for capillary dominant system possibly due to neglecting the fragmentation phenomenon in the model. Also the model over predicts abrasion for viscous dominant set up. At the end, a mechanistic approach is suggested for future modeling of agglomerate fragmentation.<br>Applied Science, Faculty of<br>Graduate
13
Rea, Brice R. "Plucking and abrasion beneath temperate plateau icefields." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239228.
Full text
14
Goksoy, M. "A study of yarn-on-yarn abrasion." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382649.
Full text
15
Trezona, Robert Ian. "Abrasion and erosion of polymeric paint coatings." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621928.
Full text
16
Thakare, Mandar Rajiv. "Abrasion-corrosion of downhole drill tool components." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/64766/.
Full textAbstract:
The present work is a Schlumberger funded PhD project entitled ‘Abrasion-corrosion of downhole drill tool components’. The objective of this project was to replicate the wear-corrosion mechanisms of tungsten carbide (WC)-based hardmetals and coatings occurring in downhole environments (pH 9-11) under controlled laboratory conditions, to identify and establish a better understanding these mechanisms and the factors influencing them so as to minimise the material wastage during service. The presence of hard and soft phases within WC-based hardmetals and coatings results in complex wear mechanisms. In addition, the presence of a corrosive environment downhole further complicates the contact conditions and can lead to accelerated surface degradation and even catastrophic failures. A Scanning Electron Microscope (SEM) investigation of worn drill-tool components revealed the presence of micro-scale (by abrasives similar size to the carbide grains i.e. less than 5 μm) and macroscale abrasion (by abrasives orders of magnitude larger in size compared to the carbide grains). The wear-corrosion testing of candidate materials was investigated using a micro-macro dual approach comprising of micro-scale abrasion testing (University of Southampton) and the modified ASTM G65 tester (National Physical Laboratories, Teddington). To mimic exposure to alkaline drilling fluids for long durations, selected samples were exposed to pH 11 NaOH solution / drilling fluid for 168 h prior to wear testing. Screening of candidate materials on the basis of their wear-corrosion performance using micro-abrasion tester was performed and WC-10Co-4Cr coating along with sintered WC-5.7Co-0.3Cr were selected for in-depth analysis and the micro-macro dual test programme. The WC-10Co-4Cr coating exposed to pH 11 and pH 7 distilled water (for comparison), revealed the presence of an intense localised corrosion in the form of ‘corrosion trenches’ due to the preferential dissolution of decarburised metallic tungsten (W), which occurred around the periphery of the carbide grains. These ‘corrosion trenches’ were found to be one-carbide deep and resulted in the carbide being held loose in the corrosion trenches. Alternatively, for the sintered WC-5.7Co-0.3Cr, exposure to pH 11 did not show any evidence of localised corrosion. However, exposure to pH 7 distilled water resulted in the preferential dissolution of the binder phase. For the first time, a modified micro-abrasion tester capable of in situ electrochemical measurements was developed to monitor the corrosion kinetics during micro-scale wear-corrosion. Interestingly, the lowest wear occurred under pH 11 conditions. It was proposed that the presence of Co(OH)2 based passive films, also detected by XPS analysis, appears to influence the rate of binder-phase removal by altering the stiffness of the abrasive-surface contact and lowering the friction between abrasives and the surface and in turn lowers the overall wear rates. This was also corroborated by the observed wear mechanism of preferential removal of the binder-phase leading to the undermining of carbides. Conversely, for the sintered WC-5.7Co-0.3Cr, despite the lack of surface passivation under similar test conditions, the wear rates were found to be independent of pH. The influence of abrasive size on the wear-corrosion performance of sprayed WC-10Co-4Cr coating was investigated using the modified ASTM G65 test. It was revealed that in addition to the size of abrasives, the wear rates are dependent on the overall wear mechanisms. In general, severe damage to the coating was caused by delamination due to the propagation of sub-surface cracks resulting in the doubling of wear rates. The sub-surface cracking of the coating increases with an increase in the abrasive size. Alternatively, for the sintered WC-5.7Co-0.3Cr, an increase in the extent of cracking in the carbide grains increased with the abrasive size. An order of magnitude increase in wear resulted from the extensive carbide cracking and the subsequent removal of the carbide grains. The dual approach successfully replicated the wear in downhole conditions by examining the influence of contact conditions and abrasive size on the wear-corrosion of WC-based sintered hardmetals and sprayed coatings to inform a better design / selection of surfaces subjected to downhole environments.
17
Lundberg, Luke. "Saponin Removal from Quinoa by Abrasion Processing." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2085.
Full textAbstract:
Quinoa is coated with a thin layer of saponins, glycosylated triterpenoids, that produce a bitter flavor when consumed. The average saponin content in commercial varietals from Bolivia average around 2.7% saponins and organoleptic testing shows the threshold for noticing a bitter flavor is below 0.12% (Medina-Meza et al., 2016). Current industrial processing methods use a combination of abrasion and turbulent water flow to remove saponin. This study will address the following research question: How will grain-to-grain and grain-to-surface abrasion affect the processing time to remove saponin from quinoa? In particular, can effective saponin removal be achieved in less than 10 minutes without washing with water?
Three different laboratory scale systems for generating grain-to-grain abrasion alone and in combination with grain-to-surface abrasion were constructed. Preliminary studies using mass balance and visual observation found the tubular system removed 4.45% of the quinoa mass in saponin containing fractions compared to the conical system (1.33%) and fluidized bed (0.62%).
After preliminary studies, a saponin estimation method was adapted and the conditions of the tubular system were determined. A randomized experiment was carried out in triplicate at three levels of time (5, 10, and 15 minutes) and mass (200, 300, and 400 grams). The effect of surface roughness in the tubular system was also evaluated. The samples were collected and saponin content in each sample was quantified using the adapted method. The saponin levels were compared to commercially processed quinoa in the market.
The processing conditions of 15 minutes at an input mass of 300 grams yielded the lowest saponin level of 0.19%. The four processing conditions of (10 minutes/200 grams, 10 minutes/400 grams, 15 minutes/200 grams and 15 minutes/300 grams) were statistically different (p
The tubular system showed promise for reducing process time and saponin content in commercially processed quinoa without washing. However, further experimentation is needed for industrial implementation. The system would provide the industry with a sustainable process with better saponin removal capacity.
18
Mezlini, Salah. "Etude de l'usure par abrasion d'alliages d'aluminium." Ecully, Ecole centrale de Lyon, 2003. http://bibli.ec-lyon.fr/exl-doc/smezlini.pdf.
Full textAbstract:
Le transport de matériaux granulaires et leurs contacts avec des surfaces métalliques génèrent souvent les dégradations de ces dernières. Partant d'une analyse des dégradations en service, l'usure par abrasion a été mise en évidence. Un suivi des dégradations en services des alliages d'aluminium a montré que la corrélation entre dureté et résistance à l'usure n'est pas toujours vérifiée. Le résultat essentiel de cette étude est une analyse de la corrélation entre la résistance à l'usure par abrasion et les différents types de durcissement. Deux familles d'alliages d'aluminium sont étudiées, les alliages à durcissement structural et les alliages écrouissables. Les simulations des dégradations ont montré que la corrélation entre dureté et usure abrasive dépend du type de durcissement et du niveau de sollicitation. Une bonne corrélation entre expérimentation et modélisation est obtenue en prenant compte la dureté après usure et non la dureté initiale. Les mesures des coefficients de frottement apparent et interfacial, couplées à des analyses microscopiques permettent de tracer une carte d'usure qui regroupe les coefficients de frottement, la géométrie de l'intendeur et les mécanismes d'usure mis en jeu<br>Transport of granular material and their contacts with metallic surface generate often degradations. Analysis of a real case damage of aluminium alloys shows that the correlation between hardness and abrasive wear is not evident. The essential result of this study is about correlation between hardness and abrasive wear resistance of aluminium alloys. Work hardened and heat-treatable aluminium alloys have been investigated. Experimental results show that the type of hardening governs any improvement of abrasive wer resistance. They show also that the correlation between hardness and abrasive wear depends on the level solicitaion. A beter correlation between abrasive wear and subsurface harness after damage has been found. Measurements of friction coefficient coupled to microscopic analysis of wear mechanisms allow to draw a card witch groups friction coefficient, indenter geometry and wear mechanisms
19
Vassou, Vassoulla. "Abrasion resistance of fibre reinforced concrete floors." Thesis, Aston University, 2003. http://publications.aston.ac.uk/14147/.
Full textAbstract:
This thesis focuses on the investigation of the abrasion resistance of fibre reinforced concrete floors at both the macro and micro levels. A literature review of the available literature concerning subjects allied to the current project is included. This highlights themes relevant to wear mechanisms and the factors influencing it: factors that affect the abrasion resistance of concrete and several test methods for assessing it; and the historical development of fibres and the properties of different fibre types and their influence on concrete. Three accelerated abrasion testers were compared and critically discussed for their suitability for assessing the abrasion resistance of concrete floors. Based on the experimental findings one accelerated abrasion apparatus was selected as more appropriate to be used for carrying out the main investigations. The laboratory programme that followed was undertaken to investigate the influence of various material and construction factors on abrasion resistance. These included mix variations (w/c ratio), fibre reinforcement, geometry, type and volume, curing method and superplasticizing agents. The results clearly show that these factors significantly affected abrasion resistance and several mechanisms were presumed to explain and better understand these observations. To verify and understand these mechanisms that are accountable for the breakdown of concrete slabs, the same concrete specimens that were used for the macro-study, were also subjected to microstructutural investigations using techniques such as Microhardness examination, Mercury intrusion porosimetry and Petrographic examination. It has been found that the abrasion resistance of concrete is primarily dependent on the microstructure and porosity of the concrete nearest to the surface. The feasibility of predicting the abrasion resistance of fibre reinforced concrete floors by indirect and non-destructive methods was investigated using five methods that have frequently been used for assessing the quality of concrete. They included the initial surface absorption test, the impact test, ball cratering, the scratch test and the base hardness test. The impact resistance (BRE screed tester) and scratch resistance (Base hardness tester) were found to be the most sensitive to factors affecting abrasion resistance and hence are considered to be the most appropriate testing techniques.
20
Mezlini, Salah Kapsa Philippe. "Etude de l'usure par abrasion d'alliages d'aluminium." (S.l.) : (s.n.), 2003. http://bibli.ec-lyon.fr/exl-doc/smezlini.pdf.
Full text
21
Voronets, Julia. "Controlled toothbrush abrasion of softened human enamels /." [S.l.] : [s.n.], 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000279103.
Full text
22
Barros, Celso de. ""Estudo da relação entre resistência à abrasão e dureza de ligas odontológicas de metais básicos para restauração metalocerâmica"." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/58/58131/tde-13112003-101112/.
Full textAbstract:
Embora haja grande exigência por restaurações estéticas livres de metal, restaurações metalocerâmicas, cujas subestruturas feitas com ligas de metais básicos, são procedimentos de rotina nos planejamentos restauradores protéticos. No entanto, a alta resistência ao desgaste destas ligas, caracterizada pela grande dificuldade de acabamento e polimento, tem sido associada à dureza, geralmente elevada. A proposta deste estudo foi avaliar resistência à abrasão e dureza de seis ligas de metais básicos (4 ligas de Ni-Cr, 1 liga de Co-Cr e 1 Ti comercialmente puro 99,5% Ti) disponíveis comercialmente para uso com cerâmica. A resistência à abrasão foi determinada pela perda de peso dos corpos-de-prova, ao longo de 4 séries de ciclos de abrasão. A dureza Rockwell 30N também foi avaliada nos mesmos intervalos. Os dados foram analisados com o nível de significância a = 0,05. O teste de regressão e correlação da resistência à abrasão e dureza mostrou que para 3 ligas de Ni-Cr (Vera Bond, Vera Bond II e Wiron 99) a linha de regressão foi descendente, indicando que um aumento na dureza correspondeu a uma redução nos valores de perda de peso, enquanto para 1 liga de Ni-Cr (Neochrom) a linha de regressão foi ascendente, indicando um aumento nos valores de perda de peso, apesar de um aumento na dureza. Por outro lado, para a ligas de Co-Cr (New Ceram) e de titânio (Rematitan), os valores de perda de peso se mantiveram constantes. As ligas avaliadas tiveram baixos coeficientes de correlação entre resistência à abrasão e dureza. A análise metalográfica revelou particularidades que podem ter sido determinantes para as taxas de desgaste de cada material. Com exceção da liga de titânio, não houve mudanças metalográficas das ligas avaliadas, durante as séries de ciclos de abrasão.<br>In spite of the demand for metal free restorations, metal ceramic restorations using base metal alloys are routine in prosthodontics. Nevertheless, the high abrasion resistance of base metal alloys, characterized by difficulty in finishing and polishing, has been related to excessive hardness. The purpose of this study was to evaluate abrasion resistance and hardness of six base metal alloys (4 Ni-Cr alloys, 1 Co-Cr alloy and 1 commercially pure Ti alloy 99.5% Ti) available commercially for use with fused porcelain. Abrasion resistance was determined by specimen weight loss along 4 series of abrasion cycles. The Rockwell 30N hardness was also determined in the same periods. Data were analyzed statistically with the level of significance set at a = 0.05. Regression and correlation analysis of abrasion resistance and hardness showed that for three Ni-Cr alloys (Vera Bond, Vera Bond II and Wiron 99) the regression lines descended indicating that an increase in hardness corresponded to a reduction in weight loss, whereas for one Ni-Cr alloy (Neochrom) the regression line ascended indicating an increase in weight loss in spite of an increase in hardness. On the other hand, for the Co-Cr alloy (New Ceram) and Ti (Rematitan), the weight loss remained constant. The alloys tested had low correlation coefficients between abrasion resistance and hardness. Microscopic analysis showed details that may have been determining for the weight loss rate of each material. With the exception of the titanium alloy, there were no metallographic changes of the alloys tested during the abrasion tests.
23
Silveira, Camila Augusto [UNESP]. "Avaliação de uma nova abordagem cirúrgico-restauradora para tratamento de recessões gengivais associadas à lesão cervical não-cariosa: estudo clínico controlado randomizado." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/132941.
Full textAbstract:
Submitted by CAMILA AUGUSTO SILVEIRA null (mila_rock_bull@hotmail.com) on 2016-01-25T17:55:14Z
No. of bitstreams: 1
tese Camila 25.01.2016 final pdf.pdf: 1354976 bytes, checksum: 4ab9699639ad08683e783abe0d66648c (MD5)<br>Approved for entry into archive by Sandra Manzano de Almeida (smanzano@marilia.unesp.br) on 2016-01-26T12:07:14Z (GMT) No. of bitstreams: 2
silveira_ca_me_sjc_int.pdf: 1354976 bytes, checksum: 4ab9699639ad08683e783abe0d66648c (MD5)
silveira_ca_me_sjc_par.pdf: 411993 bytes, checksum: b5c5a046719cd7dd1155e259de7e081c (MD5)<br>Made available in DSpace on 2016-01-26T12:07:14Z (GMT). No. of bitstreams: 2
silveira_ca_me_sjc_int.pdf: 1354976 bytes, checksum: 4ab9699639ad08683e783abe0d66648c (MD5)
silveira_ca_me_sjc_par.pdf: 411993 bytes, checksum: b5c5a046719cd7dd1155e259de7e081c (MD5)
Previous issue date: 2016-01-08<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>O objetivo do presente estudo foi avaliar um novo protocolo multidisciplinar por meio de um estudo clínico randomizado para o tratamento de recessões gengivais associadas à lesão cervical não-cariosa. Foram selecionados 40 pacientes alocados aleatoriamente em dois grupos: Grupo Teste (n=20), restauração parcial da lesão cervical e cirurgia para recobrimento radicular com enxerto de tecido conjuntivo (CTG+RP) e Grupo Controle (n=20), aplainamento da lesão cervical e cirurgia para recobrimento radicular com enxerto de tecido conjuntivo (CTG). Os grupos foram comparados quanto ao sangramento à sondagem (SS), índice de placa (IP), recessão gengival relativa (RGR), nível clínico de inserção (NIC), altura e largura das papilas (AL, LP),altura e espessura do tecido queratinizado (ATQ e ETQ), profundidade da lesão cervical (PLC), hipersensibilidade dentinária (HD) e na avaliação estética (MRES) durante um período de 6 meses. Após 6 meses, as porcentagens médias de recobrimento da altura da lesão cervical não-cariosa foram de 72,34±25,2 para o grupo teste e 74,85±33,1 para o grupo controle, sem diferença estatística entre eles. Foi notada diferença estatisticamente significante quando a hipersensibilidade cervical foi analisada. O grupo teste mostrou-se mais eficaz em 6 meses de acompanhamento na resolução desse sintoma (p=0,034). Na análise individual dos parâmetros da escala MRES, o grupo teste mostrou um melhor contorno gengival com diferença significante em relação ao grupo controle. Nos demais parâmetros, não houve diferenças significantes. Dentro dos limites do presente estudo, pode-se concluir que ambos os tratamentos foram efetivos e que a presença da restauração parcial de resina composta não interfere na taxa de recobrimento quando o retalho posicionado coronariamente associado ao enxerto de tecido conjuntivo é utilizado para o tratamento de recessões gengivais associadas à lesão cervical não-cariosa, além de proporcionar um melhor controle da hipersensibilidade dentinária e resultado estético mais harmonioso.<br>The aim of this study was to evaluate a new multidisciplinary protocol by means of a randomized controlled clinical trial for the treatment of gingival recession associated with cervical lesion non-carious. Were selected 40 patients randomly allocated to one of the following groups: Test group (n = 20), partial restoration of cervical lesion and surgery for root coverage with connective tissue graft (CTG + PR) and control group (n = 20), planning of non-carious cervical lesion and surgery for root coverage with connective tissue graft (CTG + RT). The groups were compared as to bleeding on probing (BOP), biofilm accumulation (IP), relative gingival recession (RGR), clinical attachment level (CAL), height and width of papillae (PH, PW), height and thickness of keratinized tissue (KTH and KTT), depth of the cervical lesion (CLD), dentin hypersensitivity (DH) and aesthetic evaluation (AE) for a period of 6 months. Average percentage rates of root coverage for test and control group were 72.34% and 74.85%, respectively. No significant statistical difference between test and control was observed regarding root coverage. A significant difference (p=0.034) was found for dentin sensitivity when control and test were compared. The test group showed better results regarding this parameter. The individual aesthetic analysis of MRES parameters, the test group showed a better gingival contour with a significant difference compared to the control group. When the other parameters were compared between the two groups, no difference was found. Within the limits of this study it can be concluded that both treatments were effective and that the presence of the partial restoration composite resin does not affect the root coverage when the coronally advanced flap associated with connective tissue graft is used for the treatment of gingival recession associated with non-carious cervical lesion, and provide better control of dentin hypersensitivity and harmonious aesthetic results.
24
Goossens, François. "Modélisation du processus de polissage : identification des effets et des phénoménologies induits par l'usinage abrasif." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0335/document.
Full textAbstract:
Le polissage est un procédé d’usinage par abrasion qui vise à établir une micro-géométrieprécise sur les surfaces de solides. Pour introduire les spécificités de ce procédé, un tourd’horizon sur l’usinage par abrasion est proposé. Il en découle les paramètres pouvantcaractériser une opération de polissage. Les études scientifiques existantes sont synthétisées etanalysés au regard des objectifs poursuivis. De manière à faire émerger une méthodologiepour établir des modèles et des bases de données dédiées au polissage, un banc expérimental aété mis en place et des essais ont été menés sur une tôle en inox 316L avec un abrasifstructuré de forme pyramidale. Une méthode de mesure de l’usure des pyramides abrasives aété mise au point. Les premiers essais ont mis en évidence la nécessité pour les grains abrasifsd’exercer sur la matière une pression supérieure à une valeur minimale. Un modèle deconsommation matière issu de la loi de Preston a été présenté et validé par des essais. L’étudepar des plans d’expériences factoriels complets des efforts induits, de la rugosité au traversdes critères proposés par la norme ISO et de la mouillabilité a permis de mettre en évidencel’influence prépondérante de la taille des grains abrasifs. Par contre, la pression exercée parles grains, leur vitesse de défilement et le taux d’usure des pyramides abrasives n’ont qu’unrôle secondaire sur ces critères. Ces résultats constituent de précieuses indications pour lesbureaux des méthodes devant établir des gammes de polissage<br>The polishing is a process of manufacturing by abrasion which aims at establishing a precisemicro-geometry on the surfaces of solids. To introduce the specificities of this process, anoverview on the manufacturing by abrasion is proposed. As a result, the parameters which cancharacterize an operation of polishing are identified. The existing scientific studies aresynthesized and analysed with regard to the pursued objectives. For the testing, an experimenttest bench was developed. The proposed methodology is applied on the polishing process ofthe AISI 316L using pyramidal abrasive belts. A measurement method of the abrasivepyramids wear is finalized. A method of measuring the abrasive pyramids wear is provided. Aremoving material rate model based on the Preston's law is presented and experimentallyvalidated. A study based on the design of experiment is conducted using as output the cuttingforces, the roughness and the wettability criteria. The results point out the dominatinginfluence of the size of the abrasive grains. On the other hand, the study indicates the fact thatthe applied pressure on the abrasive grains, the belt speed and the abrasive level do not playan important role on the previously cited characteristics. On the other hand, the studyhighlights that the applied pressure on the abrasive grains, the belt speed and the abrasivelevel do not have a significant effect on the previously cited characteristics. These resultsconstitute valuable indications for the industrial polishing process optimization
25
Petrov, Adrien. "Modélisation mathématique de procédés d'usinage: abrasion et mouillage." Phd thesis, Université Claude Bernard - Lyon I, 2002. http://tel.archives-ouvertes.fr/tel-00005277.
Full textAbstract:
Ce travail de thèse est consacré à l'étude d'un modèle viscoélastique avec des contraintes unilatérales, modélisé comme un matériau de Kelvin-Voigt. Le chapitre un est consacré au cas monodimensionnel: on approche la solution du problème par pénalisation, ce qui conduit à un théorème d'existence d'une solution faible. Un résultat de régularité des traces permet de montrer que la solution est forte. Le chapitre deux comporte un schéma numérique dont on montre la convergence vers une solution faible. Les chapitres trois et quatre permettent de construire une solution forte dans un milieu monodimensionnel semi-infini, pour laquelle on sait établir un bilan d'énergie: les pertes sont purement visqueuses. Le problème est réduit à une inégalité variationnelle au bord faisant intervenir un opérateur pseudodifférentiel dont le terme principal est une dérivation d'ordre 3/2. Les chapitres cinq et six comportent des théorèmes de trace pour une équation des ondes amorties et pour un opérateur de viscoélasticité dans un demi-espace, avec application aux solutions fortes.
26
Wilson, Andrew. "Fluvial bedrock abrasion by bedload : process and form." Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/265496.
Full textAbstract:
Bedrock channels are a key component of the landscape. Pluvial bedrock incision sets the local base level, the boundary condition for hill slope processes, transmits tectonic and climatic signals throughout the landscape and transports sediments to sedimentary basins. Bedrock river networks are also responsible for the texture and relief of an unglaciated landscape, and in flexural landscapes bedrock channels significantly effect rates and patterns of erosional unloading and consequently long-term sediment fluxes to basins. This thesis investigates the mechanism and morphological expression of one of the key mechanisms of erosion in bedrock river incision: abrasion by bedload. Both long term landscape evolution and physical process based models of bedrock incision would benefit from a better understanding of the controls and behaviour of the abrasion process in natural substrates and settings. A field .campaign documenting evidence of bedrock channel erosion identified upstream facing convex surfaces as a common morphology found in bedrock rivers in Taiwan. An asymmetry of morphology and microscopic surface texture (microsurface texture) related to stream flow direction were identified as core characteristics of this bedrock bedform. A conceptual model is suggested explaining the formation of these features by impact abrasion from bedload particle streams. The three dimensional change of ten upstream facing convex surfaces were captured using three dimensional laser scanning in combination with a novel coreferencing system. This passive, non-invasive study established the kinematics of the eroding surface. Spatial variation of erosion is strongly linked to the aspect of the eroding surface in relation to the mean channel flow direction. The convex, upstream facing surface is found " to be the location of significantly elevated erosion relative to the companion downstream facing and horizontal lee surfaces. The process of fluvial bedrock abrasion by bedload was isolated in a flume study. In a parallel approach, the microsurface texture and morphological evolution of rock blocks abraded by cobble and pebble grade bedload was investigated. The control by grain calibre, grain lithology, bedrock lithology and initial form of the obstacle were investigated. A causal link between process and form was robustly established and some insights were gained into the importance of impact angle, impact frequencies and velocities of impact of a bedload particle stream. Deformation caused by single impacts of polished quartz spheres onto flat, polished marble plates was determined using optical white light interferometry in a controlled laboratory study. The influence of sphere diameter, impact angle and impact velocity were investigated and empirical relationships between these variables determined. In all 782 impact craters measured in this study, no significant erosion occurred. A final study examined the deformation of a surface that was repeatedly impacted until erosion occurred. Surface changes were mapped on an impact by impac~ basis and are described by statistical parameters. The marble plate underwent an incubation period during which no erosion was observed. At a critical number of impacts, catastrophic failure occurred in the deformed surface of the marble plate resulting in the generation of a wear particle (erosion). Abrasion by bedload was determined to be a key process in fluvial bedrock incision and the morphological signature of its action constrained. The outcomes of these projects require that channel roughness, bedload particle streams and properties of particle and substrate be factored into future physically based models of bedrock channel erosion for an accurate representation of channel evolution. A simple conceptual model of the nucleation and propagation of upstream facing convex surfaces originating at a lithological boundary is presented combining insights from all projects.
27
Lafleur, Jean-Philippe. "A study of abrasion in steel during comminution." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103656.
Full textAbstract:
Comminution is a process used in mineral processing for the size reduction of mined material, to permit effective handling, separation and recovery. The equipment used is kinetically complex, with very high-energy impacts and high forces, leading to great amounts of abrasive wear. It is desired to develop a better understanding of these processes, to both measure them and increase comminution while reducing wear. The Steel Wheel Abrasion Test is a laboratory technique used to generate controlled, abrasive three-body wear. By altering the applied force, rotational speed of the wheel and abrasive agent used in the SWAT, the wear behaviour of a material can be quantified. High-stress wear, which occurs when abrasive material is degraded during the test, can replicate the processes occurring in comminution systems. This work has found that abrasive wear will increase with increasing input energy into the tribological interaction. This wear can be linked to the energy input into the system, through the measurement of applied forces, wheel rotational speed and generated torque. This results in the development of a specific abrasion energy, EAS, which provide an energy metric for the abrasion process. Furthermore, the breakage induced in the abrasive particles can also be quantified and evaluated, generating a comminution metric, the specific comminution energy, ECS. These indices can then be linked, to develop an understanding of systems where comminution and abrasion occur concurrently.<br>La communition est un procédé utilisé dans l'industrie minéralurgique pour la réduction de taille d'un minerai, afin de permettre le transport, la séparation, la récupération et l'extraction de ce matériel. L'équipement utilisé pour cette tâche est complexe, soumis à des forces élevées et des impacts violents, ce qui génère une quantité importante d'usure. Une plus grande connaissance des processus de comminution et d'usure est nécessaire pour pouvoir évaluer leur amplitude, dans le but de favoriser la comminution tout en minimisant l'usure. Le test d'abrasion par roue d'acier (SWAT) est une technique de laboratoire utilisée pour générer de l'usure abrasive à trois composantes. En contrôlant la force appliquée, la vitesse de rotation de la roue et l'agent abrasif employé lors du test SWAT, il est possible d'évaluer la réponse d'une surface à l'abrasion. L'usure de haut stress, générée dans les systèmes où les agents abrasifs sont fracturés, peut répliquer les procédés présents dans l'équipement de communition. Ce projet a trouvé que l'usure abrasive augmente avec une augmentation de l'énergie investie dans l'interaction tribologique. Cette usure peut être liée à l'énergie du système, en mesurant les forces appliquées, la vitesse de rotation de la roue et la torsion générée. Ces valeurs peuvent être utilisées pour calculer une valeur spécifique d'énergie d'abrasion, EAS, qui agit comme indice pour le procédé d'abrasion. De plus, la fragmentation créée dans les particules abrasives peut être évaluée, pour générer un indice de communition, ECS, l'énergie spécifique de communition. Ces deux indices peuvent être liés, pour rejoindre les procédés de communition et d'abrasion.
28
Brown, I. F. "Abrasion and friction in parallel-lay rope terminations." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596954.
Full textAbstract:
Ropes made from parallel aramid yarns have been used for many years due to their light weight, good electrical properties and utilisation of the material's stiffness. The standard termination for these parallel-lay ropes is a "spike-and-barrel" developed by the rope manufacturer. The terminations perform very well under static loading but fail due to abrasion of the rope near the nose of the spike when exposed to cyclic stresses. Spike-and-barrel terminations for parallel-lay ropes are much more complex than they first appear. The functioning of the termination is heavily influenced by geometry, the material properties of both the termination and fibre, and the frictional properties. Any alteration to one of these factors alters the behaviour of the whole termination. Over their 25 year history, Parafil terminations have evolved into a sophisticated design which works well most of the time. To improve on their performance this study has looked inside the terminations and exposed hitherto unknown mechanisms and processes of slip and wear. No straightforward analysis is possible because the simplifying assumptions mask the subtleties of the design. The use of a modified Howell's equation for friction, τ = <I>a</I>σ<SUP>β</SUP>, is proposed here as a valid means of modelling the friction between polymeric materials. This re-expression in terms of stress, enables its use in a finite element analysis. Experiments on Kevlar 49 yarns over aluminium capstans were performed to determine the stick and slip coefficients of friction. Experiments on pads of 1000 yarns were also performed to determine the non-linear transverse stress-strain properties of Kevlar 49. Two sets of transverse moduli can be derived, one for first-loading, and a much stiffer set for unloading-reloading. This data is integrated into the analysis via subroutines written by the engineer. Using the Kevlar 49-on-aluminium abrasion tests performed here, a general formula has been devised for lifetime, in terms of contract pressure, amplitude of slip and thickness to be abraded. This formula is coupled with the calculated severities in 6 and 60 tonne terminations, to predict lifetimes for ropes under various cyclic regimes. These predictions are very close to those reported in the literature.
29
Halim, Mahdi Hassan. "Truck tyre tread rubber : compounding and abrasion resistance." Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/6743.
Full text
30
Alshabbani, Haydar Swiry Rahi. "Metal matrix composites with diamond for abrasion resistance." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/22944/.
Full textAbstract:
Metal matrix composites (MMCs) have been used in many applications (such as automotive, aerospace and construction) for many decades. Recently, there have been interesting developments in this type of composite, applying them in electronic and thermal applications such as with semiconductors, in electronic packaging and heat sinks. This is particularly the case for composites of a metal matrix with diamond which are considered a modern sub-class of metal matrix composites. However, while the thermal properties are exceptional, this class of composites has not been extensively examined for mechanical and tribological behaviour, and it may be possible to apply these composites in practical applications, especially those that require extreme mechanical and tribological strength, for example cutting resistance for security applications. Therefore, this research looks for a composite material consisting of metal matrix and diamond particles, which resists abrasive cutting. This progresses through a series of steps, developing methods to process the material, understanding the mechanics of abrasive behaviour and optimizing the composite structure to resist abrasive cutting. Gas Infiltration (GI) casting under gas pressure has been applied to metal matrices with relatively low melting point (aluminium (Al) and tin (Sn)) to obtain a significant penetration of the metal into a preform of diamond particles. Different diamond particle sizes (63-75, 212-250, 420-500 μm) were used to strengthen the Al matrix and diamond coated with a thin Ti layer was used to attempt to enhance the bonding forces between the aluminium matrix and diamond. Al-1 wt. % Mg as a matrix alloy was utilised to investigate the possible effect of Mg on bonding phases and to reduce the surface tension of molten aluminium during the infiltration process. Epoxy was also used as a matrix with diamond in this research by gravity infiltration. Tribological and microstructural tests were performed on the samples, and the results show that the surface modification (Ti coating) of diamond particles has an important role for enhancing the bonding between the aluminium matrix and diamond reinforcement as is apparent under SEM observation, thus improving wear resistance. The coating layer works to either catalyse the graphitisation of diamond surfaces to then dissolve carbon in the metal, or reacts at the diamond surfaces to form carbide crystallites at the interface. This may be one of the reasons contributing to the bonding between the different matrices and diamond. The presence of some of these phases was indicated with XRD patterns and Raman spectra. The principal characterization method was by abrasion cutting tests, which have been carried out on all the samples made. One particle size range, 420-500 μm, of diamond coated by Ti, has been used to manufacture composites with different matrices (titanium (Ti), nickel )Ni(, copper)Cu(, tin)Sn) and epoxy) using different production methods (PM and SPS) for the transition metal matrices due to their high melting points. The abrasion cutting tests of these composites showed that the bonding between the metal matrix and diamond reinforcement and the processing temperature, have an important role in enhancing the abrasion wear resistance of composites, rather than the hardness of matrices.
31
Kent, Anthony Clifford. "The mechanics of abrasion relating to household cleaning." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6954/.
Full textAbstract:
Abrasion of polymer surface films or coatings in an everyday occurrence, whether in the home, work or industry. As a result a wide variety of polymer films can be found on surfaces. Despite the numerous applications, three body thin film abrasion appears a niche area of study and as a result under-researched. This investigation focuses on identifying, characterising and quantifying the abrasive wear of a baked dehydrated castor oil deposit formed on stainless steel. The primary aim of this project is to understand how the fundamental properties of the liquid abrasive cleaning system contribute to the material removal. Investigations have primarily been carried out using a reciprocating linear tribometer for the cleaning and a profilometer to measure the wear. The wear of the baked oil film was found to largely follow the established Archard wear equation of sliding distance and load, despite the fact it was derived to describe two body and not three body wear. However the wear rate was not inversely proportional to hardness and there were significant effects when parameters not in the Archard equation are considered. IN particular changing the speed, viscosity, particle size and distribution all had an impact on the wear.
32
Rutherford, Keith Leslie. "New methods for characterising abrasion and erosion resistance." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627429.
Full text
33
Fasahat, F., R. Dastjerdi, and M. R. M. Dastjerdi. "Abrasion Resistance of Ag/SiO2/PA6 Nanocomposite Fabrics." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35638.
Full textAbstract:
In recent decades, polymeric nanocomposites have been widely used in chemical, automobile and aero industries due to their low weight and smoothness. Abrasion resistance is a vital property in variable ap-plications of polymeric composites. Here, to investigate the wear resistance of nylon 6 nanocomposite fab-rics, melt spun yarns were filled with different concentrations of Ag/SiO2 nanoparticles and the wear prop-erties of weft knitted nanocomposite and pure samples were evaluated. Results disclosed that the wear re-sistance of composite fabrics containing nano-particles increased considerably in comparison to pure one. Therefore, nanoparticles can play an important role in improving the nanocomposite wear resistance.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35638
34
OLIVEIRA, Marcelo dos Anjos. "Desgaste abrasivo do aço Hadfield com diferentes teores de carbono em abrasômetro do tipo pino-disco." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18671.
Full textAbstract:
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-04-27T15:18:52Z
No. of bitstreams: 2
license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5)
Marcelo Oliveira.pdf: 7846435 bytes, checksum: 4659cf7d50095ccabdf49ebcc00f0bba (MD5)<br>Made available in DSpace on 2017-04-27T15:18:52Z (GMT). No. of bitstreams: 2
license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5)
Marcelo Oliveira.pdf: 7846435 bytes, checksum: 4659cf7d50095ccabdf49ebcc00f0bba (MD5)
Previous issue date: 2016-08-31<br>A presente pesquisa teve como objetivo, investigar o efeito do teor de carbono e do
tamanho do abrasivo na resistência ao desgaste e no fenômeno de encruamento
superficial de quatro aços Hadfield. Para esse estudo, foi montado, o equipamento pino
contra disco, e, como abrasivo utilizou-se lixas de ferro, com o tamanho médio entre 36
µm e 93 µm. Para o alcance do objetivo proposto foram delimitados materiais e
métodos, a saber: (a) montagem do abrasômetro pino-disco a partir de um dispositivo
desativado disponibilizado pelo LFS-USP; (b) confrontar resultados experimentais –
dois materiais (Aço 1045 e alumínio 6351) foram submetidos a ensaios realizados na
UFPE e USP para fins de estudos comparativos; (c) avaliação da influência de
parâmetros do ensaio – três abrasivos com diferentes tamanhos de partículas e diferentes
cargas foram submetidos e avaliados mediante o desgaste abrasivo; (d) avaliação do
comportamento de diferentes composições do aço Hadfield perante ensaios de
abrasividade – aços contendo quatro diferentes teores de carbono foram submetidos a
ensaios com lixas #220 e #320; (e) análise das superfícies desgastadas – após os ensaios
dos materiais, as superfícies foram realizadas análises por microscópio eletrônico de
varredura (MEV) das superfícies desgastadas. Os resultados obtidos com o equipamento
na metodologia empregada tiveram uma boa reprodutibilidade. Foram observadas
diferenças nos resultados entre os equipamentos da UFPE e da USP. Quanto a este
tópico, o desgaste abrasivo do aço Hadfield foi influenciado pelo teor de carbono
apresentando uma relação em que maiores teores demonstraram menor efeito de
desgaste, diferentes tamanhos de abrasivo ocasionam um efeito de encruamento
significativo, onde se observou o ganho de dureza em aços com menores teores de
carbono. Contudo, foi apresentada uma oscilação do efeito no abrasivo #320. As
micrografias revelaram microssulcos e microcortes provenientes do ensaio e não foram
observadas diferenças nas marcas de desgaste quando utilizados tamanhos diferentes de
partícula abrasiva. Ao final, chegou-se a conclusão de que os resultados obtidos
demonstram que o teor de carbono influência na resistência ao desgaste do aço e
consequentemente no encruamento superficial do aço. Observa-se também a influência
do tamanho do abrasivo e carga aplicada o ensaio.<br>This research aimed to investigate the effect of the carbon content and the size of the
abrasive in the wear resistance and surface hardening phenomenon four Hadfield steel.
For this study , has been assembled , the disc against pin device and abrasive was used
iron sandpapers, with average size between 36 m and 93 micrometers. To achieve the
proposed objectives were defined materials and methods, namely: (a) mounting the pindisk
abrasômetro from a disabled device provided by the LFS-USP; (b) comparing
experimental results - two materials (1045 steel and aluminum 6351) were submitted to
tests performed at university and USP for purposes of comparative studies; (c)
evaluation of the influence of the test parameters - Three abrasive particles with
different sizes and different loads were submitted and evaluated by the abrasive wear;
(d) assessment of the behavior of different steel compositions Hadfield before
abrasiveness tests - steels containing four different carbon contents were subjected to
tests with sandpaper # 220 and # 320; (e) analysis of the worn surfaces - after the tests
of materials different analyzes were performed by scanning electron microscope (SEM)
of worn surfaces. The results obtained with the equipment in the methodology
employed had good reproducibility. There were differences in results between the
equipment and the UFPE USP. On this topic, the abrasive wear Hadfield steel was
influenced by carbon having a relationship in which higher levels showed less wear
effect, different abrasive sizes cause a significant strain hardening effect, which was
observed gain hardness steel with lower carbon content. However, an oscillation of the
abrasive effect on the # 320 was presented. The micrographs revealed microssulcos and
microcuts from test and differences were observed in wear marks when using different
sizes of abrasive particle. In the end, came to the conclusion that the results show that
the influence of carbon content in the wear resistance of steel and consequently the
surface of the steel hardening. It is also observed the influence of abrasive size and load
applied to the test.
35
CAUBET, CHRISTOPHE. "Abrasion dentaire physiologique et pathologique : etude dans une usine d'abrasifs." Toulouse 3, 1989. http://www.theses.fr/1989TOU31204.
Full text
36
Aslantas, Onur. "A Study On Abrasion Resistance Of Concrete Paving Blocks." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605709/index.pdf.
Full textAbstract:
Concrete block pavement (CBP) can be an alternative pavement to asphalt and concrete pavements. CBP is formed from individual concrete paving blocks (CPBs) that fit next to one another on a suitable sub base leaving a specific joint space among them to be filled with jointing sand.
CBP differ from other pavements according to their mechanical behavior, manufacturing technique, structural design, installation technique and structural behavior. For a serviceable pavement all of these subjects have to be studied. The literature about the mechanical behavior of CPBs is not adequate. This study aims to determine the performance of CPBs formed from different mixes prepared with a white portland cement.
For this purpose, 10 mixes with different cement contents and W/C ratios and 2 mixes from a commercial CPB manufacturer were tested. The compressive strength,
tensile splitting strength, abrasion resistance, density and % water absorption tests were performed on each mix at 7, 14, 28 days.
It was concluded that, the cement content in the mix, optimum water volume for a given cement content, the way the manufacturing equipment is operated and their interaction was effective on the mechanical properties of CPBs. It was also observed that there was no handicap to stop the abrasion resistance test at 8*22 revolutions instead of 16*22 revolutions given in TS 2824.
37
Jones, Jeremy. "Abrasion Characteristics of Ring-Spun and Open-End Yarns." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20011115-182006.
Full textAbstract:
<p> Jones, Jeremy. Abrasion Characteristics of Ring-Spun and Open-End Yarns. (Under the direction of Dr. Pam Banks-Lee and Dr. William Oxenham.) In the early 1980s, widespread claims in the knitting industry suggesting that the use of open-end yarns significantly increased the wear of mechanical components, especially knitting needles. Since then, many studies have attempted to explain this phenomenon and have yielded widely varying results. A study was conducted to compare the yarn properties of open-end yarn to ring-spun yarn. Identical yarns of varying parameters including yarn type, yarn count, and twist multiple were produced from the same raw cotton stock to eliminate variability in raw material. These yarns were tested for abrasiveness on a Lawson-Hemphill CTT (Continuous Tension Transport) tester. The device passes the yarn over a wire and records the length of yarn required to sever the wire. For this study the CTT was encoded to abrade a fixed length of yarn over the wire. The wire was then observed with both a Hitcahi ESEM (Environmental Scanning Electron Microscope) and a digital imaging microscope. The resultant images were examined for attrition and the abrasion values were evaluated using statistical analysis. It was confirmed that an increase in yarn count corresponded to a decrease in abrasion. Twist multiple had a noticeable effect on abrasion although the trends between yarn types, and yarn counts were inconsistent. Open-end yarn abrasion values were only slightly greater than their ring-spun counterparts, contradicting the claims of the knitting industry.<P>
38
Scholl, Milton R. "Development of intermetallic-hardened abrasion-resistant weld hardfacing alloys /." Full text open access at:, 1986. http://content.ohsu.edu/u?/etd,95.
Full text
39
Molloy, Padraig. "Plastic and brittle mechanisms in single-point glass abrasion." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46454.
Full text
40
Elwell, David W. J. "Toughness and abrasion resistance of high alloy cast iron." Thesis, Aston University, 1986. http://publications.aston.ac.uk/11866/.
Full text
41
Teixeira, Symone Cristina [UNESP]. "Avaliação da microinfiltração marginal em restaurações de classe V em resina composta em dentes bovinos: efeito de diferentes equipamentos para preparos cavitários e sistemas adesivos." Universidade Estadual Paulista (UNESP), 2000. http://hdl.handle.net/11449/114070.
Full textAbstract:
Made available in DSpace on 2015-01-26T13:21:31Z (GMT). No. of bitstreams: 0
Previous issue date: 2000-03-06Bitstream added on 2015-01-26T13:30:17Z : No. of bitstreams: 1
000134871.pdf: 7061870 bytes, checksum: 73e133b2649ba2fd2f69348825cc9651 (MD5)<br>O objetivo desse trabalho foi avaliar in vitro a microinfiltração marginal de cavidades de classe V preparadas com turbina de alta rotação (AR), jato abrasivo (AB), ultra-som (US) e laser de Er:YAG (LA) e restauradas com um sistema adesivo multi-passos e um auto-condicionante. Foram selecionados 160 incisivos bovinos para prepare das cavidades na face vestibular, com margem gengival localizada na junção esmalte-cemento e margem oclusal em esmalte. Os materiais utilizados foram Scotchbond Multi-uso Plus/3M (SBMUP), Etch&Prime 3.0/Degussa (EP) e a resina composta Z1 00/3M. Os dentes foram divididos em oito grupos de vinte, de acordo com equipamento e sistema adesivo empregado: a) AR + SBMUP; b) AR + EP; c) AB + SBMUP; d) AB + EP; e) US+ SBMUP; f) US+ EP; g) LA+ SBMUP; e h) LA+ EP. Os dentes restaurados foram armazenados a 37°C par 6 dias, termociclados (500: 5-55°C) e colocados em solução de Rodamina B a 2% por 24 horas. Em seguida foram seccionados e avaliados em lupa estereomicroscópica para determinar o grau de microinfiltração segundo uma escala de 0 a 4. Os dados foram submetidos aos testes estatísticos de Sinais de pastas de Wilcoxon, Kruskai-Wallis e Tukey. Houve diferença estatisticamente significante entre as margens, com maior microinfiltração na cervical; o melhor selamento marginal foi obtido no grupo US/SBMUP; não houve diferença estatisticamente significante entre os preparos cavitários realizados com laser de Er: YAG e alta-rotação e alta-rotação e abrasão a ar; os maiores valores de microinfiltração foram obtidos no grupo AB/EP<br>The aim of this study was to evaluate in vitro the marginal microleakage of class V prepared with high-speed (HS}, air abrasion (AA), ultrasound (US) and Er:YAG /aser(LA), and restored with multi-step or self-etching adhesives systems. One-hundred-sixty incisives bovine teeth were selected for the cavity preparation on the buccal surface with the gingival margin at the enamel-cement junction and occlusal margin in enamel. The materials Scotchbond Multi Purpose/3M (SBMUP) and Etch&Prime 3.0/Degussa (EP) and Z10013M composite resin were used in this study. The teeth were divided in eigth groups with 20 teeth in each froup according to the equipment and to the adhesive system used: HS + SBMUP; HS +EP; AA +SBMUP; AA + EP; US+ SBMUP; US+ EP; LA+ SBMUP; LA + EP. The restored teeth were stored at 37CC for 6 days, thermocycled (500: 5-55 C) and kept in a 2% Rodamine B solution tor 24 hours. After this they were seccioned and evaluated through stereomicroscope in order to determine the micro/eakage degree according to 0-4 score. The data were submitted to the Wilkoxon, KruskaiWal/ is and tukey statistical tests. There was significant statistical difference among the margins with the highest microleakage degrees in the cervical area; the best marginal sealing was with the US + SBMUP group. There was no significant statistical difference among the cavity preparations made with the Er:YAG laser and high-speed and high-speed and air abrasion. The highest microleakage values were found in the AA +EP group
42
Muzilli, Marcelo 1972. "Efeito de metodos de polimento na rugosidade e dureza Vickers de ceramicas para cobertura." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289567.
Full textAbstract:
Orientador: Lourenço Correr Sobrinho<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba<br>Made available in DSpace on 2018-08-13T01:39:57Z (GMT). No. of bitstreams: 1
Muzilli_Marcelo_D.pdf: 34149055 bytes, checksum: 91212ba7ea6406d835e270899c5d9256 (MD5)
Previous issue date: 2009<br>Resumo: O objetivo deste estudo foi avaliar o efeito do método de polimento na rugosidade e na dureza Vickers de doze cerâmicas utilizadas para cobertura, após serem submetidas ao desgaste abrasivo. Foram confeccionados quarenta discos de cada cerâmica, cor de esmalte, com 8 mm de diâmetro e 2 mm de espessura. O pó cerâmico de cada marca comercial (CERAMCO, CERCON, FINESSE, IPS D.SIGN, IPS ERIS, VINTAGE HALO, VISION, VISION ESTHETIC, VITA VM7, VITA VM9, VITA VM13 e WILL CERAM) foi aglutinado com o líquido modelador indicado e aplicado em uma matriz metálica bipartida. Após a sinterização e o esfriamento, os discos foram desgastados, simulando uma situação de ajuste oclusal, com ponta diamantada 3098 F e 3098 FF (KG Sorensen), e divididos em 4 grupos (n=10): Grupo P - polimento com abrasivos do sistema Shofu; Grupo PP - polimento com sistema Shofu + pasta diamantada (6 mm - KG SORENSEN); Grupo PG - polimento + glaze e Grupo G - glaze (Controle). Os corpos-de-prova foram levados ao rugosímetro Surf-Corder para mensuração da rugosidade de superfície, utilizando o parâmetro Ra. Foram feitas três mensurações em cada corpo-de-prova. A dureza Vickers foi efetuada no aparelho HMV-2 (Shimadzu), calibrado com carga de 9,8 N atuando por 15 segundos. Cinco penetrações foram feitas em cada corpo-de-prova e a média calculada. Os dados foram submetidos à Análise de Variância e ao teste de Tukey (5%) e mostraram que as cerâmicas Finesse, VM7, VM9, VM13 e IPS Eris não tiveram influência do método de
polimento na dureza Vickers. Os menores valores de dureza Vickers foram obtidos pelas cerâmicas Vintage Halo e VM7 no grupo P; Cercon, Vintage Halo, VM9 e Ceramco no grupo PP; Cercon no grupo PG e Ceramco, Cercon, Will Ceram e Vision Esthethic no grupo G. Os métodos de polimento tiveram influência na rugosidade em todas as cerâmicas utilizadas. Os menores valores de rugosidade foram obtidas pelas cerâmicas VM9, VM13, VM7, IPS Eris, Ceramco e Vintage Halo, no grupo P; Will Ceram, VM7, VM13 e Vintage no grupo G e Will Ceram, VM7 e Vision no grupo PG. O grupo PP promoveu os menores valores de rugosidade não diferindo entre as cerâmicas utilizadas.<br>Abstract: The aim of this study was to evaluate the polish method influence on surface roughness and Vickers hardness number of the twelve dental ceramics, after abrasive grinding. Forty enamel ceramic disks with 8 mm in diameter and 2.0mm thickness were made. The ceramic powder for each brand (CERAMCO, CERCON, FINESSE, IPS D.SIGN, IPS ERIS, VINTAGE HALO, VISION, VISION ESTHETIC, VITA VM7, VITA VM9, VITA VM13 and WILL CERAM) was agglutinated with the appropriate modeling liquid and applied on a bipartite metallic matrix. After the sinterization and cooling, the disks were submitted to a simulation of oclusal adjustment with 3098 F and 3098 FF diamonds burs (KG SORENSEN), and divided into four groups (n=10): Group P - Shofu polishing system; Group PP - Shofu polishing system + diamond paste (6mm - KG SORENSEN); Group PG - Shofu polishing system + glaze; and, Group G - glaze (control). The roughness was measured on a Surf-Corder machine using Ra parameter. Three
measurements were made for each specimen and the average calculated. The Vickers hardness number was measured with HMV 2 microhardness tester (Shimadzu), with a load of 9,8 N applied for 15 seconds. Five measurements were made for each specimen. The dates were submitted to ANOVA and Tukey's test (5%) and showed that only the ceramics FINESSE, VM7, VM9, VM13 and IPS ERIS weren't the influence of surface treatment on Vickers hardness. The lowers hardness values were obtained by Cercon, Vintage Halo and VM7, in group P; Cercon, Vintage Halo, VM9 and Ceramco in Group PP; Cercon, in Group PG;
Ceramco, Cercon, Will Ceram and Vision Esthetic, in Group G. The roughness
suffered the influence of the surface treatment in all the ceramics that were used.
The lowers roughness values were obtained by VM9, VM13, VM7, IPS Eris,
Ceramco and Vintage Halo, in Group P; Will Ceram, VM7, VM13 e Vintage in
Group G and Will Ceram, VM7 e Vision in Group PG. The Group PP promoted the
lowers roughness averages that didn't show any difference statistic among all the
ceramics.<br>Doutorado<br>Materiais Dentarios<br>Doutor em Materiais Dentários
43
Italiani, Flávia de Moraes. "Efeito do íon ferro na prevenção da erosão dentária: estudos in vitro e in situ." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/25/25142/tde-18082010-103048/.
Full textAbstract:
Este projeto teve como objetivos investigar o efeito do íon ferro (Fe+2), associado ou não ao íon flúor (F-), na redução da erosão do esmalte e da dentina bovinos, bem como desenvolver e avaliar um dentifrício enriquecido com Fe+2 para a prevenção da erosão associada à abrasão. Foram realizados 4 subprojetos: (1) Determinação do efeito protetor de concentrações crescentes do Fe+2 (0 a 120 mmol/L) associadas ou não ao F- (0 a 4 g/mL), contra a dissolução do pó de esmalte bovino in vitro; (2) Avaliação, in vitro, do efeito protetor do Fe+2 a 10 mmol/L contra a dissolução mineral da superfície do esmalte bovino; (3) Desenvolvimento e avaliação, in vitro, de dentifrícios fluoretados enriquecidos com diferentes concentrações de Fe+2, visando à prevenção da perda mineral do esmalte bovino; (4) Avaliação, in situ, do efeito inibidor do dentifrício acrescido de Fe+2 e F- na desmineralização do esmalte e dentina bovinos sadios ou previamente erodidos. As variáveis de resposta utilizadas foram a quantificação da perda de fósforo (colorimetria) e o desgaste (perfilometria, m) para os subprojetos 1 e 2, e 3 e 4, respectivamente. Os dados foram submetidos à análise estatística (p<0,05). Para o Subprojeto (1), a ANOVA a 2 critérios e o teste de Bonferroni revelaram que soluções contendo Fe+2 a 1,25, 2,5, 5,0, 10, 15 e 30 mmol/L reduziram significativamente a dissolução do pó de esmalte bovino em 18, 18, 23, 35, 35 e 55%, respectivamente, em comparação ao controle (sem Fe+2). Na presença de F-, o efeito do Fe+2 na inibição da dissolução do esmalte foi reduzido, não havendo efeito sinérgico entre estes íons nas condições testadas. No Subprojeto (2), a ANOVA a 2 critérios e o teste de Bonferroni, mostraram uma redução significativa na desmineralização da superfície do esmalte bovino em torno de 30 a 40%, quando se utilizou solução de Fe+2 a 10 mmol/L. No Subprojeto (3), a ANOVA revelou diferença significativa entre os grupos (Placebo, 1100 g/mL de F-, Crest®, Fe+2 1,0 mg/g, Fe+2 2,5 mg/g, Fe+2 5,0 mg/g, F- (1100 g/mL) + Fe+2 1,0 mg/g, F- (1100 g/mL) + Fe+2 2,5 mg/g e F- (1100 g/mL) + Fe+2 5,0 mg/g) (F=4,734, p<0,0001). O menor desgaste (0,48±0,24 m) foi apresentado pelo grupo em que foi utilizado o dentifrício contendo 1100 g/mL F- e 5 mg/g Fe+2. No Subprojeto (4), para o esmalte hígido a ANOVA a 2 critérios revelou uma diferença significativa entre os dentifrícios, (F=21,72, p<0,0001), mas não entre as condições (só erosão, erosão + slurry, erosão + abrasão) (F=1,20, p=0,32) e nem para a interação entre ambos (F = 1,04, p=0,41). O teste de Bonferroni revelou que os blocos que receberam o dentifrício contendo Fe+2 e F- apresentaram valores de desgaste significativamente menores quando comparados aos blocos submetidos aos demais dentifrícios, os quais não diferiram significativamente entre si. Para a dentina hígida, o esmalte previamente erodido e a dentina previamente erodida, o mesmo padrão foi seguido, apesar destes dois últimos terem apresentado valores de desgaste maiores que aqueles observados para os blocos hígidos.<br>The aims of this study were to investigate the effect of iron (Fe+2) associated or not to fluoride (F-) on the reduction of bovine enamel and dentin erosion, as well as to develop and evaluate a dentifrice containing Fe+2 to prevent erosion associated to abrasion. Four subprojects were done: (1) In vitro determination of the protective effect of increasing Fe+2 concentrations (0 to 120 mmol/L) associated or not to F- (0 to 4 g/mL) against the dissolution of powdered enamel; (2) In vitro evaluation of the protective effect of 10 mol/L Fe+2 against the mineral dissolution of superficial bovine enamel; (3) Development and in vitro evaluation of fluorided dentifrices containing different Fe+2 concentrations in order to prevent the mineral loss of bovine enamel; and (4) In situ evaluation of the effect of a dentifrice containing Fe+2 and F- on the demineralization of sound or previously eroded bovine enamel and dentin. The response variables were quantification of phosphate loss (colorimetry) and tooth wear (perfilometry, m) for the subprojects 1 and 2, and 3 and 4, respectively. Data were submitted to statistical analyses (p <0.05). In subproject (1), two-way ANOVA and Bonferronis test revealed that solutions containing 1.25, 2.5, 5.0, 10.0, 15.0 and 30.0 mmol/L Fe+2 significantly reduced the dissolution of powdered enamel at 18, 18, 23, 35, 35 and 55%, respectively, in comparison to control (without Fe+2). In the presence of F-, the effect of Fe+2 on the dissolution of enamel was reduced and no synergistic effect between these ions was observed in the tested conditions. In Subproject (2), two-way ANOVA and Bonferronis test showed a significant reduction on surface demineralization of bovine enamel (around 30-40%), when the solution containing Fe+2 at 10 mmol/L was used. In Subproject (3), ANOVA revealed a significant difference among the groups (Placebo, 1,100 g/mL F, Crest®, 1.0 mg/g Fe+2, 2.5 mg/g Fe+2, 5.0 mg/g Fe+2, F- (1, 100 g/mL) + 1,0 mg/g Fe+2, F- (1100 g/mL) + 2,5 mg/g Fe+2 and F- (1,100 g/mL) + 5,0 mg/g Fe+2) (F=4,734, p<0,0001). The lowest wear (0.48±0.24 m) was observed when the dentifrice containing F + Fe was used. In Subproject (4), for sound enamel, two-way ANOVA revealed a significant difference among the dentifrices, (F=21.72, p<0.0001), but not among the conditions (erosion only, erosion + slurry, erosion + abrasion) (F=1.20, p=0.32) or for the interaction of both (F = 1.04, p=0.41). The Bonferronis test revealed that the blocks which received the dentifrice containing Fe+2 and F- presented significantly lesser wear when compared to the blocks submitted to the other dentifrices, which did not differ significantly among each other. As for sound dentin as well as for previously eroded enamel and dentin, the same pattern was obtained but the latter two presented wear values higher than those seen for the sound blocks.
44
Martins, Samira Branco. "Influência do tamanho da partícula, do jateamento prévio à sinterização e do envelhecimento na resistência mecânica de uma zircônia estabilizada por ítria." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/155943.
Full textAbstract:
Submitted by Samira Branco Martins (samirabmartins@foar.unesp.br) on 2018-08-30T19:44:38Z
No. of bitstreams: 1
TESE DOUTORADO SAMIRA .pdf: 933881 bytes, checksum: 1ebe4097c1b2d6665a4be82cc94f2dfa (MD5)<br>Rejected by Marley Cristina Chiusoli Montagnoli (marley@foar.unesp.br), reason: Por favor, fazer as seguintes correções:
- inserir a ficha catalográfica no arquivo de sua tese;
- quando for preencher metadados, preencher o campo Agência de fomento. on 2018-09-04T12:52:59Z (GMT)<br>Submitted by Samira Branco Martins (samirabmartins@foar.unesp.br) on 2018-09-06T18:29:33Z
No. of bitstreams: 1
TESE DOUTORADO SAMIRA .pdf: 1082516 bytes, checksum: 012f9fe0b3e970650b71802c977af92d (MD5)<br>Rejected by Marley Cristina Chiusoli Montagnoli (marley@foar.unesp.br), reason: A ficha catalográfica está fora do padrão.
Quando for inserir no seu arquivo observar em opções de colagem e escolher a opção que não desconfigure a sua ficha.
Qualquer dúvida procure a Biblioteca de sua unidade. on 2018-09-06T19:06:06Z (GMT)<br>Submitted by Samira Branco Martins (samirabmartins@foar.unesp.br) on 2018-09-06T20:03:50Z
No. of bitstreams: 1
TESE DOUTORADO SAMIRA.pdf: 939079 bytes, checksum: 5d37e78b11c143842a751fbaf6498aa2 (MD5)<br>Approved for entry into archive by Marley Cristina Chiusoli Montagnoli (marley@foar.unesp.br) on 2018-09-10T17:35:24Z (GMT) No. of bitstreams: 1
martins_sb_dr_arafor.int.pdf: 879795 bytes, checksum: 35bf73c7fbec804a07b0b28fe05ae668 (MD5)<br>Made available in DSpace on 2018-09-10T17:35:24Z (GMT). No. of bitstreams: 1
martins_sb_dr_arafor.int.pdf: 879795 bytes, checksum: 35bf73c7fbec804a07b0b28fe05ae668 (MD5)
Previous issue date: 2018-08-03<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Pouco se sabe sobre o efeito do jateamento pré-sinterização da zircônia na sua resistência mecânica, sob condições de envelhecimento. Este estudo avaliou a influência do tamanho da partícula, do momento do jateamento e do envelhecimento na resistência mecânica de uma zircônia estabilizada por ítria. Quatrocentos discos de uma zircônia estabilizada por ítria pré-sinterizados foram alocados como segue: sem jateamento; jateamento com partículas de óxido de alumínio (Al2O3) de 50 µm ou 120 µm antes (50/PRÉ ou 120/PRÉ) ou após (50/PÓS ou 120/PÓS) sua sinterização. Os discos foram não envelhecidos (24h) ou envelhecidos por: ciclagem mecânica (CM); envelhecimento hidrotérmico (EH) ou CM+EH, totalizando 20 grupos (n=20). Os espécimes foram submetidos ao teste de resistência à flexão biaxial (RFB) e, posteriormente, foram analisados fractograficamente. A análise de difração de raios-X (DRX) foi realizada em determinadas condições para caracterizar cristalograficamente o efeito do jateamento na zircônia. Os dados de RFB (MPa) foram analisados por ANOVA a 3 fatores e pós teste de Games Howell (α=0,05). Também foi realizada análise de Weibull. A RFB e a resistência característica (σ0) dos grupos 120/PÓS, envelhecidos ou não, foram significativamente maiores que as dos demais grupos jateados, e estatisticamente similares ou maiores que as dos respectivos grupos sem jateamento. Em contrapartida, o grupo 120/PRÉ/não envelhecido e todos os grupos 50/PRÉ apresentaram os menores valores. Em todos os grupos, o defeito inicial se originou na superfície submetida à tração. Nem o jateamento, nem o envelhecimento (exceto o grupo 50/PÓS/CM+EH) reduziram a confiabilidade da zircônia em relação à dos respectivos grupos controles. O jateamento promoveu um aumento do conteúdo de fase monoclínica, enquanto a sinterização zerou essa fase. O jateamento da zircônia antes da sinterização teve pior desempenho para RFB em comparação ao realizado após sua sinterização, sob os meios de envelhecimentos. A RFB e σ0 foram fortemente determinadas pelo tamanho da partícula e pelo momento do jateamento, enquanto o envelhecimento agiu apenas quando a zircônia foi jateada antes da sinterização.<br>Little is known about the effect of air-abrasion before zirconia sintering on its strength, under aging challenge. This study aimed to verify the influence of the air-abrasion moment (before or after zirconia sintering), particle size (50 or 120 μm) and aging on the mechanical strength of a Y-TZP ceramic. Four hundred pre-sintered zirconia discs were allocated as follows: non-air-abraded; air-abraded with 50 μm or 120 μm Al2O3 particles before (50/BS or 120/BS) or after sintering (50/AS or 120/AS). The discs were non-aged (24h) or aged by: mechanical cycling (MC); hydrothermal aging (HA) or by both methods (MC+HA), totaling 20 groups (n=20). Specimens were subjected to biaxial flexural strength test (BFS). Fractographic analysis was performed to identify the fracture origin. The X-ray diffraction analysis (XRD) was performed under certain conditions to characterize the crystallographic effect of air-abrasion on the zirconia. The BFS data (MPa) were analyzed by ANOVA and Games Howell post hoc test (α=.05). Weibull statistics was also applied. The BFS and the characteristic resistance (σ0) of the 120/AS groups, aged or not, were significantly higher than those of the other air-abraded groups, and statistically similar or higher than the respective groups without air-abrasion. In contrast, the 120/BS/non-aged group and all those 50/BS presented the lowest values. In all groups, the initial defect had its origin on the tensile stress side. Neither air-abrasion nor aging (except for 50/AS/MC+HA) reduced the zirconia reliability compared with the respective controls. Air-abrasion promotes an increase in the monoclinic phase content, while sintering zeroed this phase. Air-abrasion before zirconia sintering yields worse performance for BFS than after sintering, under aging challenges. The BFS and σ0 were strongly determined by the particle size and air-abrasion moment, while aging acted only when the zirconia was air-abraded before sintering.
45
Goeldel, Benoit. "Étude et mise en œuvre d'un moyen flexible pour le rodage de carter cylindre de moteur à combustion interne." Phd thesis, Paris, ENSAM, 2013. http://pastel.archives-ouvertes.fr/pastel-00910324.
Full textAbstract:
Le procédé de rodage par pierres abrasives est actuellement utilisé pour produire en grande série des chemises de carter cylindre avec des propriétés fonctionnelles spécifiques. La qualité de forme, la rugosité et l'aspect des surfaces ainsi rodées déterminent grandement les performances mécaniques et écologiques des moteurs. Le processus de rodage, mécaniquement complexe, fait intervenir des machines complètement dédiées et optimisées pour les rodages classiques. Après une étude détaillée des machines de production actuelles, de leurs performances et de leurs limites, l'objectif de recherche de flexibilité du procédé pour l'industriel Renault s'est traduit par deux développements : une modélisation de l'abrasion avec une simulation du procédé pour mieux le comprendre et la conception d'un prototype de machine de rodage à hautes performances pour tester d'autres méthodes de rodage.La simulation est basée sur la double discrétisation de l'espace-et du temps et sur un modèle de coupe original. La discrétisation de l'espace permet de représenter à une échelle macroscopique le rodoir et la pièce à usiner et de tenir compte des contacts locaux entre eux. Les propriétés microscopiques et mésoscopiques de la surface rodée sont étudiées à cette échelle. La discrétisation temporelle autorise la prise en compte de la cinématique de la machine. Le modèle de coupe repose sur l'interaction des courbes de portance du rodoir et de la chemise. Son exploitation au niveau macroscopique permet de prédire l'enlèvement de matière, la force de contact locale ainsi que l'aspect de la surface rodée et leurs évolutions au cours du rodage. Cette simulation est validée par de nombreuses expériences.Ce document présente la conception, la réalisation et la mise au point d'un prototype de machine de rodage avec des actionneurs électriques à performances dynamiques élevées. Une commande numérique permet le pilotage synchronisé de la rotation et du battement et autorise l'interpolation de trajectoires. L'expansion radiale peut être pilotée en position ou en force. Nous avons proposé de nouvelles trajectoires originales dans l'objectif d'augmenter la productivité du procédé et dans le but de générer de nouvelles textures.
46
Redmalm, Göran. "Dentifrice abrasivity." Stockholm : Kongl Carolinska Medico Chirurgiska Institutet, 1987. http://catalog.hathitrust.org/api/volumes/oclc/15730783.html.
Full text
47
Chan, Kit-ping Cordelia, and 陳潔萍. "Comparing the effectiveness of a new innovative desensitizing paste to a home-used desensitizing toothpaste in reducing dentine hypersensitivity among Chinese adults." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206444.
Full textAbstract:
This study aimed to compare the effectiveness of an 8% arginine and calcium carbonate in-office desensitizing prophylaxis paste with that of a home-use toothpaste having the same active ingredients in reducing dentine hypersensitivity. The study was a randomized controlled clinical trial involving 55 subjects who had at least one tooth with sound exposed dentine on the cervical region of the buccal surface displaying hypersensitivity. The subjects were recruited from students and staff, other than those from the Faculty of Dentistry, of The University of Hong Kong. After receiving scaling performed by a dental hygienist at baseline, subjects were randomly assigned to either the in-office desensitizing prophylaxis paste treatment group or the home-use desensitizing toothpaste group. Clinical assessments of dentine hypersensitivity to tactile and to thermal stimuli were performed prior to the treatment at baseline, week 4 and week 12 by a blinded examiner and subjective global assessments of dentine hypersensitivity were recorded. The responses of the subjects to both stimuli were recorded by using a pain score scale from 0 to 10 (from no pain to unbearable pain). Reponses to both tactile and thermal hypersensitivity assessments in the home-use desensitizing toothpaste group showed statistically significant differences between baseline and week 12 (tactile: 2.4 vs. 0.9; cold: 5.8 vs. 3.5, both p<0.05). There was a statistically significant difference in the tactile assessment scores (1.8 vs. 1.0, p<0.05) but not in the thermal hypersensitivity assessment scores (5.5 vs. 5.3, p>0.05) for the in-office desensitizing prophylaxis paste group. There was also a statistically significant difference in the change in thermal assessment scores between the two groups (in-office: -0.2 vs. home-use: -2.3, p<0.05) but not in the tactile hypersensitivity assessment scores (in-office: -0.9 vs. home-use: -1.2, p>0.05). There were no statistically significant differences in global subjective responses to external stimuli in the telephone interviews. Daily use of an 8% arginine and calcium carbonate toothpaste was able to reduce dentine hypersensitivity over 12 weeks but a single in-office application of prophylaxis paste of similar content was not able to provide instant and long-lasting benefits for subjects with a mild-to-moderate degree of dentine hypersensitivity.<br>published_or_final_version<br>Dentistry<br>Master<br>Master of Philosophy
48
Euzenat, Charly. "Contributions à la simulation de l’enlèvement de matière par abrasion." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST059.
Full textAbstract:
La réalisation des pièces mécaniques à forte valeur ajoutée implique des temps d'usinage conséquents et nécessite parfois une finition des surfaces fonctionnelles par abrasion pour atteindre les spécifications requises. La bonne définition des paramètres de la gamme de fabrication joue un rôle important dans l'obtention l'état de surface final sur les pièces produites. Dans ce contexte, la maîtrise des exigences est encore réalisée de manière empirique.La thèse sur le polissage des surfaces fonctionnelles et plus particulièrement sur la prédiction et la simulation réaliste des effets des procédés d'abrasion sur la topographie des surfaces. Les travaux proposés contribuent à étudier de nouvelles méthodes de simulation pour l'abrasion. Plus particulièrement, l'enjeu scientifique de ces travaux est de créer une rupture vis-à-vis des simulations classiques à base de maillages, par l'utilisation de méthodes particulaires, et d'en évaluer les performances dans ce contexte. Les résultats de simulation obtenus dans le cadre d'essais d'indentation et de rayage ont été comparés à des essais et sont concluants. Cependant, les temps de simulation sont trop grands pour envisager une simulation d'abrasion complète mettant en œuvre le passage de centaines de grains abrasifs.Pour pallier ces difficultés, le développement d'un modèle d'abrasion basé sur la représentation implicite des surfaces a été mené. Le procédé d'abrasion est modélisé en utilisant ce formalisme de représentation des surfaces. Une gamme de fabrication complète allant de l'usinage à l'abrasion est simulée avec succès et est validée expérimentalement. Les modèles étudiés pourraient être une base au développement d'un outil de simulation industriel. L'apport des simulations au profit de l'automatisation des opérations d'abrasion et de l'optimisation des gammes de fabrication pourrait permettre d'augmenter la productivité et la qualité des pièces mécaniques<br>The production of mechanical parts with high added value involves significant machining times and sometimes requires the functional surfaces to be finished by abrasion in order to achieve the required specifications. The correct definition of the parameters of the manufacturing process plays an important role in obtaining the final surface finish on the parts produced. In this context, the control of involved parameters is still carried out empirically.The thesis focuses on the polishing of functional surfaces and in particular on the prediction and realistic simulation of the effects of abrasion processes on surface topography. The proposed work contributes to the study of new simulation methods for abrasion. More specifically, the scientific challenge of this work is to create a breakthrough with conventional simulations, using meshless methods, and to evaluate their performance in this context. The simulation results obtained in indentation and scratching tests have been compared to experimental results and are in agreement. However, the simulation times are too long to envisage a complete abrasion simulation involving the passage of hundreds of abrasive grains.To overcome these difficulties, the development of an abrasion model based on the implicit representation of surfaces was carried out. The abrasion process is modelled using this surface representation formalism. A complete manufacturing process from machining to abrasion is successfully simulated and experimentally validated. The models studied could be a possible foundation for the development of an industrial simulation framework. The contribution of simulations to the automation of abrasion operations and the optimization of manufacturing processes could help to increase the productivity and quality of mechanical parts
49
DiSantis, Nicholas E. "Rub, fold, and abrasion resistance testing of digitally printed documents /." Online version of thesis, 2007. http://hdl.handle.net/1850/4489.
Full text
50
Ablal, Manal Ahmed. "Investigations on dental erosion and dental abrasion and related studies." Thesis, University of Liverpool, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569890.
Full textAbstract:
Dental erosion has increased in prevalence over the last decades. The wider availability and frequent consumption of acidic soft drinks and other acidic substances is thought to be one of the main aetiological factors. It is also well established that this frequent exposure of dental hard tissue surfaces to such acidic attacks renders the outermost enamel layer softened and readily susceptible to be rubbed away by mechanical forces. While most of the studies emphasised on the role of toothbrushing, the effect of oral musculature, especially the tongue, is considered to play a major part in abrading pre - eroded enamel surfaces. Despite the attempts to in vitro simulate tongue abrasion; there is a lack in the literature regarding its role as a causative factor in tooth surface loss. The work presented in this thesis is divided into six chapters. The first chapter includes a general review on tooth wear, enamel erosion and abrasion in particular, referring to the various techniques commonly used to quantify enamel mineral and surface loss. Chapter 2 investigates the erosive effect of some commercially available alcoholic beverages (alcopops) on enamel surfaces. The results from that study showed that alcopops have a significant potential to cause erosion similar to that of orange juice. Further, in the same chapter, a group of dental materials commonly used to mount tooth specimens in erosion studies were examined for their fluorescence properties. It was found that some of those materials exhibited fluorescence activity that affected the quality of images using equipments such as quantitative light - induced fluorescence. Chapter 3 demonstrates that the application of tooth whitening products is not without risking enamel surfaces to undergo erosion and that chlorine dioxide bleaching products, although to a lesser extent, can cause surface demineralisation similar to that caused by hydrogen peroxide. In chapter 4, the effect of simulated tongue abrasion on pre - eroded enamel surfaces is investigated over different periods of erosion and abrasion cycles. Results from that study revealed a significant amount of mineral and surface loss after the application of tongue simulated movements particularly when erosion times were prolonged. Chapter 5 describes an in vitro study where the super saturation of artificial saliva with calcium ions has greater remineralisation properties than the specially formulated Pronamel® mouth wash, deionised water and modified artificial saliva without calcium. The mouthwash has superior remineralisation effect while the two latter solutions, particularly the modified artificial saliva without calcium, caused the greatest mineral loss and lesion depth. Chapter 6 embraces two studies; an in situ part investigating the effect of tongue abrasion on pre - eroded enamel surfaces in addition to an in vitro pilot study investigating the period required for those eroded surfaces to be physically lost to form craters. The findings from the in situ study shows that short and cyclic exposure of enamel specimens to acidic drinks followed by mechanical abrasion by the tongue results in an increased mineral and surface loss. This effect was more recognised on specimens localised opposite to the upper anterior teeth. Also, labial and palatal enamel surfaces have similar mineral and surface loss. Enamel craters formed after as early as 1 week and showed a significant depth after 4 weeks of exposure to orange juice. In conclusion, it has been shown that the tongue could exert an amount of pressure sufficient to remove pre - eroded enamel surfaces.